I found my old reMarkable 2 tablet, bought in 2021, unused for 4 years. It was in a sorry state: cloud sync failing with error 0, software update failed. I googled the error and found a forum post with a "fast solution". SSH into the tablet over Wi‑Fi (or USB) and set the clock; then I could download a software update.

After the first update the cloud sync returned HTTP 400. The journal said "Unable to sync. Please update this application…". The first update only brought the tablet to 3.11.2.5 and wouldn’t update further. Restarting swupdate.service and update-engine.service allowed a second update to 3.27.3.0, the latest version.

Starting with 3.22, SSH over Wi‑Fi is disabled. Re‑enable it with rm‑ssh-over‑wlan or delete the marker file. Cloud sync still failed, so I turned on the optional web server to import and export files. I backed up the xochitl config, set "Web Interface Enabled=true", restarted xochitl.service, and used curl to upload PDFs.

The tablet is now fully functional. If you encounter similar issues, the same steps—reset time, restart update services, re‑enable SSH, and use the web interface—should bring your device back to life.