Litespeedcache key domain registration error

I used for some time the Litespeedcache plugin with WordPress, but now I found a problem with the key domain registration. Seems that something are injecting code into the REST API where it should not do this, in technical support words.

My server technical support says this:

They sayed:

Your domain ‘fotov60.com’ seems to not be responding properly in the URL indicated in the screenshot.

When I access https://www.fotov60.com/wp-json/litespeed/v1/token, it shows the following:

<!-- commented two forms options page and also remove add_theme_page options page and also remove include link -->{"_res":"ok"}

This is not a valid JSON response; it should be like the last part:

{"_res":"ok"}

I would recommend starting your investigations from there.

Someone have idea what are happenning and how to fix it? My web is https://www.fotov60.com

The possibility is that another plugin is interfering with the Litespeed Cache plugin and causing the communication issue. Deactivating all other plugins and then reactivating them one by one can help identify the culprit.

@wk0189713 thanks for youre answer. In the end, it turned out that the person developing my blog had added some lines of code to the functions.php file that blocked the plugin for testing purposes and forgot to remove them when finished. Fortunately, he remembered it during our conversation, and once removed, it worked again.