For now, Siri won’t keep track of your Apple Music ratings
He adds that “It’s been working great, including the start of today, with Siri responding “Okay, I’ve rated it a [###] out of 5” or “Okay, I’ve rated it [###] stars.” Some time today that stopped working. The only responses I get now are “Sorry, I can’t do that” or “Sorry, I can’t help you with that”. All other Music related commands still seem to work. I can rate the songs manually via the ••• menu.”
Apple Community Specialist acts like Siri’s actions are due to a bug
If the issue remains, the Community Specialist says to sign out and back in. Go to Settings > Tap on Your Name > Media & Purchases > Sign out. Once you’re signed out, restart your device and go back to Settings > Tap on Your Name > Media & Purchases > and sign in.” Unfortunately, this will temporarily remove any music you’ve saved for offline listening forcing you to once again download all the music you saved to listen to offline.
The final comment from the Community Specialist says that if the issue persists, then you will need to contact Apple Support for further assistance.