Suddenly issue with RSS feed from MediaPortal

Hello,

for a few days I get an error within Mediaportal when I put the RSS link to trakt calendar.
If I insert the link into InfoService plugin of MediaPortal and click Save, I get this:

I didn’t change anything, suddenly it happens, until some days ago it worked all fine.
What could it be?

Checking the log I have this message:

Remote server error: (403). Not permitted.