We are troubleshooting an issue impacting community login, and it may be intermittently unavailable. Sorry for any inconvenience.
Try the following:
1. Create a backup (or just archive) of the config file (in this directory: C:\Users\CurrentUser\AppData\Local\PTC\).
2. Delete the current config file (in this directory: C:\Users\CurrentUser\AppData\Local\PTC\).
3. Run Mathcad Prime again.