MetaMask won't open in Firefox

I keep getting this message when opening MM in Firefox:

MetaMask had trouble starting.

This error could be intermittent, so try restarting the extension.

Error details

An unexpected error occurred

It has done this for months and contacting metamask support has been useless.

The problem is that one of my wallets can't be accessed by my seed phrase. The only way I can get to it is in the Firefox Metamask.

That means I can't risk uninstalling and reinstalling or it might be gone.

Fortunately it is only for about 3% of my portfolio and some staking rewards, so it will be an expensive lesson but not catastrophic.

If any has solved this that would be a huge help!