Error occurred

Hello,

I am going through some maintenance on my blog and I have a problem with this new plugin I downloaded. When I go to Tool > Regenerate Thumbnails > Regenerate Thumbnails for all the attachments I get the following error message:
” Unable to fetch a list of attachment IDs to process from the WordPress REST API. You can check your browser’s console for details.”

p.s. I don’t know if this is related or not to the problem, but I downloaded another plugin that keeps the blog in maintenance mood.

I hope you can help me figure this out.

Thank you,
Enzo.

The page I need help with: [log in to see the link]