0. Did you upgrade from older version? If so, please uninstall and install again.
Or are you using an old version Firefox? This addon is only tested on Firefox >= 100, if lower than this, please upgrade.

1. Have you ever try to "click outside" any input after enter something in an input? This should trigger saving action. (You can scroll to the ""MOST bottom"" of the setting page, it should show a notification "Modifications to Settings are Saved"....Maybe I should replace it with OS notification and it should be more clear for user...)

2. I've tested this addon on various Firefox on lots of devices and OS (Linux & Windows, even on Android), and the save action of settings is workable in all of them. Therefore I totally cannot imagine what is the problem you encountered, if these tips still not fixed, please contact with me with email, maybe use a Chrome Remote Desktop or TeamViewer to see what's going on.

3. The last but not the least, addons.mozilla.org is very not suitable for bug report, because the both sides cannot reply to each other more than 1 time, totally useless as a bug tracker. So if you encounter similar problem on other addons, me recommended to use support site or email provided by the addon instead of leave a review directly, that's very difficult to resolve problem for developer. If developer cannot get the description of a reproducible environment of user's bug, it's a nearly unusable bug report.