Ever since I upgraded my phone to Pixel 11, incoming calls have been going directly to voicemail. I’ve attempted all possible solutions, and it seems the problem might be related to my Monzo SIM card? I only receive SMS messages about missed calls. Could the problems be related to the modem on the Pixel phone?
I’ve actually just gone to check and I’m now getting the same error message as you about call forwarding ‘failed to read data’. My calls (incoming and outgoing) are working fine though but I have definitely been able to access that information before (and I even have a screenshot when it was working). I have raised a ticket in the help section of the app, suggest you do the same so they can get the technical team to investigate - they did investigate the reported data issues previously and were able to resolve so do log a ticket so they have sight of it.
The call forwarding did work on Monzo Mobile at one point as I grabbed a screenshot at the time (shown here). Something has changed though as I’m getting the same error message now about it failing to read the information from the network so to check SIM card and connection