What to do when the Prism panel is open and connected but every request fails. Covers jsx-engine-unavailable, host-not-loaded, host-not-readable, host-missing, host-stale and engine-unreachable.

This page covers one specific failure: the panel is open, your AI client is connected, and yet every request fails. Nothing you do in After Effects changes the outcome.

If your AI client cannot see Prism at all, that is a different problem — see Troubleshooting instead.

The short version

This is an install problem, not something open in After Effects. Restarting After Effects on its own will not fix it.

The usual cause is that Prism was installed for all users, so its files belong to the system account while After Effects runs as you.

The fix is to reinstall Prism for your user account only, then restart After Effects.

You do not need to collect logs. Current versions of the panel report the cause to us automatically.

The errors this page covers

Your AI client will show one of these. They are different measurements of the same situation: After Effects is there, but it is not running Prism's script.

Error	What it means	What to do
`host-not-readable`	The script file exists, but After Effects cannot read it. Most common cause: a system-wide install.	Reinstall for your user account
`host-missing`	The script file is not on disk. The install did not complete.	Reinstall for your user account
`host-not-loaded`	After Effects is responding, but it never loaded Prism's script. This is not a dialog.	Reinstall for your user account
`host-stale`	After Effects still has an older copy of the script in memory.	Restart After Effects
`engine-unreachable`	After Effects will not run scripts at all. This one can be a dialog.	Clear the dialog
`jsx-engine-unavailable`	The older, single label used before Prism could tell these apart. Update the panel.	Update the panel
`not-connected`	No panel is bridged to your session.	Open the panel: Window → Extensions → After Effects MCP

Reinstall for your user account

Adobe extensions can be installed in two places: one that belongs to you, and one that belongs to every user on the machine. When Prism lands in the machine-wide location, its files are owned by the system account. After Effects runs as you — so it can see the files and still not be allowed to read them.

Nothing about that is visible from inside After Effects, which is why it can look like the panel is broken when the install is the problem.

Prism can live in either of two places. Yours, or the machine's:

	Belongs to you	Belongs to every user
macOS	`~/Library/Application Support/Adobe/CEP/extensions`	`/Library/Application Support/Adobe/CEP/extensions`
Windows	`%APPDATA%\Adobe\CEP\extensions`	`%CommonProgramFiles%\Adobe\CEP\extensions`

You want the left-hand column.

Quit After Effects completely

Not just the panel. After Effects loads extensions once at launch, so it must be fully closed for any of this to take effect.

Remove the machine-wide copy

If a Prism folder exists in the right-hand location above, delete it. This is the copy After Effects cannot read.

Install for your user account

Reinstall the panel, choosing the per-user option in your ZXP installer rather than installing for all users. It should land in the left-hand location.

Reopen After Effects

Window → Extensions → After Effects MCP. Then ask your AI client "Tell me about my current composition." A description of your comp means it is working.

If you use a managed or shared machine and cannot write to your own user folder, contact your IT administrator, or email support@oneprism.io and our support team will work through it with you.

More than one copy is installed

If Prism has been installed twice — for example once for all users and once for you — After Effects may load either one. Behaviour then changes between sessions for no visible reason.

Quit After Effects, remove the older copy from the locations listed above, then reopen. Keep exactly one.

When it really is a dialog

engine-unreachable is the only error here that a dialog can cause. After Effects stops running scripts entirely while a modal window is waiting for an answer, including one that has opened on a second monitor or behind the main window.

Check every display for an open After Effects dialog and dismiss it. If nothing is open, restart After Effects.

For every other error on this page, a dialog is not the cause, and looking for one costs time.

Update the panel

jsx-engine-unavailable is the older label. It was a single error used for all of the situations above, which meant it could not tell you which one you had.

Newer versions of the panel measure the cause and name it. If you are seeing jsx-engine-unavailable, download the current panel from the License Portal and reinstall it for your user account.

What Prism now does on its own

Recent versions of the panel changed how this is handled:

The panel measures the cause instead of guessing it. It checks whether the script file exists, whether your user account can read it, whether After Effects loaded it, and whether After Effects is running scripts at all — and reports which of those is false.
Each result maps to one fix, which is what the table above lists.
When something is wrong, the panel reports it to us automatically, along with the relevant Adobe and Prism logs. You do not have to find or send anything.
The wording you see comes from our server, so the guidance improves without you reinstalling anything.

Still stuck

If you have reinstalled for your user account, removed any duplicate copy, and restarted After Effects, and requests still fail, email support@oneprism.io with the error name from the table above and what you were asking for. Our support team will answer.

For anything about your plan, licence key, freeing a device, or downloading the panel again, the License Portal is the fastest route.

Troubleshooting: connection checks and everything else.
Getting set up: the full install.
Connect your AI client: per-client connection setup.

Prism cannot reach After Effects