No Connection to Browser: dial unix /tmp/alfred-firefox.501.sock: connect: no such file or directory

Alfred 4.2.1; Firefox Assistant 0.2.1; Firefox 83.0; Alfred Integration 1.1.2; Catalina 10.15.7

I have two Macs with exactly the above setup;
On one, I installed the Alfred Firefox Integration without trouble, on the second I now cannot get it to work:

```
[03:28:29.671] Firefox Assistant[Script Filter] Script with argv 'ase' finished
[03:28:29.672] ERROR: Firefox Assistant[Script Filter] Code 1: 03:28:29 workflow_paths.go:143: [warning] info.plist not found. Guessed: /Users/fnl/Documents/Dropbox/Configs/Alfred/Alfred.alfredpreferences/workflows/user.workflow.2BBC9FED-93A4-49F1-B4B8-2698E78F073E
🍺
03:28:29 workflow.go:327: ----- Firefox Assistant/0.2.1 (AwGo/0.20.2) ------
03:28:29 actions.go:83: loaded URL action "Open in Chrome" from "~/Documents/Dropbox/Configs/Alfred/Alfred.alfredpreferences/workflows/user.workflow.2BBC9FED-93A4-49F1-B4B8-2698E78F073E/scripts/Open in Chrome.sh"
03:28:29 actions.go:83: loaded URL action "Open in Default Application" from "~/Documents/Dropbox/Configs/Alfred/Alfred.alfredpreferences/workflows/user.workflow.2BBC9FED-93A4-49F1-B4B8-2698E78F073E/scripts/Open in Default Application.sh"
03:28:29 actions.go:83: loaded URL action "Open in Firefox" from "~/Documents/Dropbox/Configs/Alfred/Alfred.alfredpreferences/workflows/user.workflow.2BBC9FED-93A4-49F1-B4B8-2698E78F073E/scripts/Open in Firefox.sh"
03:28:29 actions.go:83: loaded URL action "Open in Safari" from "~/Documents/Dropbox/Configs/Alfred/Alfred.alfredpreferences/workflows/user.workflow.2BBC9FED-93A4-49F1-B4B8-2698E78F073E/scripts/Open in Safari.sh"
03:28:29 update.go:210: 9m16.681611s since last check for update
03:28:29 client.go:248: searching bookmarks for "ase" ...
03:28:29 rpc_client.go:36: [ERROR] dial unix /tmp/alfred-firefox.501.sock: connect: no such file or directory
03:28:29 workflow.go:342: ------------------ FATAL ERROR -------------------
03:28:29 workflow.go:343: Cannot Connect to Extension : goroutine 1 [running]:
runtime/debug.Stack(0xc000147990, 0x1, 0x1)
/usr/local/opt/go/libexec/src/runtime/debug/stack.go:24 +0x9d
github.com/deanishe/awgo.(*Workflow).Run.func2(0xc000138000)
/Users/daj/pkg/mod/github.com/deanishe/awgo@v0.22.1/workflow.go:343 +0xe7
panic(0x140f940, 0x1544170)
/usr/local/opt/go/libexec/src/runtime/panic.go:679 +0x1b2
main.mustClient(0x14c15b5)
/Users/daj/Code/Alfred/alfred-firefox-assistant/rpc_client.go:37 +0xb4
main.runBookmarks(0xc0000c2030, 0x0, 0x0, 0x0, 0x0)
/Users/daj/Code/Alfred/alfred-firefox-assistant/client.go:249 +0xc1
github.com/peterbourgon/ff/ffcli.(*Command).Run(0x1831c40, 0xc0000c2030, 0x0, 0x0, 0x183a601, 0x2)
/Users/daj/pkg/mod/github.com/peterbourgon/ff@v1.7.1-0.20200101221212-72e429b6ad42/ffcli/command.go:96 +0x248
github.com/peterbourgon/ff/ffcli.(*Command).Run(0x1832500, 0xc0000c2010, 0x3, 0x3, 0x14b6453, 0x9)
/Users/daj/pkg/mod/github.com/peterbourgon/ff@v1.7.1-0.20200101221212-72e429b6ad42/ffcli/command.go:90 +0x1f1
main.run()
/Users/daj/Code/Alfred/alfred-firefox-assistant/main.go:144 +0x191
github.com/deanishe/awgo.(*Workflow).Run(0xc000138000, 0x14d4a18)
/Users/daj/pkg/mod/github.com/deanishe/awgo@v0.22.1/workflow.go:357 +0x2af
main.main()
/Users/daj/Code/Alfred/alfred-firefox-assistant/main.go:149 +0x39
03:28:29 workflow.go:344: ---------------- END STACK TRACE -----------------
03:28:29 feedback.go:468: Sent 1 result(s) to Alfred
03:28:29 workflow.go:375: [ERROR] Cannot Connect to Extension
03:28:29 workflow.go:378: Get help at https://github.com/deanishe/alfred-firefox/issues
03:28:29 workflow.go:401: ------------------- 5.937233ms -------------------
[03:28:29.681] Firefox Assistant[Script Filter] {
"variables": {
"AW_SESSION_ID": "PQJB0DNB94Q85SOZIQUAT3J5"
},
"items": [
{
"title": "Cannot Connect to Extension",
"valid": false,
"icon": {
"path": "icons/error.png"
}
}
]
}
```

If I run the `server.sh` script from a terminal, it starts and even gets the searches from Alfred, but times out as it does not connect to Firefox.
And the Firefox extension always insists it is "disconnected".
Also, `ffass workflow:register` finishes successfully.

Removing and reinstalling the workflow as well as restarting the machine also did not help.
Any ideas what I can try next?