It was working until recently. Now it displays a message advertising the subscription and I can't close that and use the add-on.

Seems to be false advertising about being freemium as it appears to require a subscription now.

Plain unusable

It is not free, and you can not try it for free to see if it is worth it.

Over 300k credits expired after one year

Not working on latest version of FF 115.0, did uninstall and reinstall, also disabled and enabled few times. Developer should do some basic testing

Is no longer free, you have to pay for using it

you have to pay to use it