Been like this for a week or two now. Express just refuses to sync new updates on my Forerunner 235. Tried on my laptop and desktop. I deleted a few watch faces in case it was a storage issue, it's not. Can't do anything to fix this. I'm giving it a few more days before I return this thing. I really want this thing to work, but my lord are you (Garmin) making this hard.
What is the exact error message you are receiving in Garmin Express? Is it an update that is failing to download to your Forerunner 235 or your activities are failing to upload to Garmin Connect? Without knowing the exact issue (subject mentions updates but post only discusses syncing) I can recommend a few different FAQs that should assist you.
If it is a problem syncing activities up to Garmin Connect:
What should I do if I am unable to sync my mass storage fitness device using Garmin Express?
If it is a problem downloading updates in Garmin Express:
What should I do if I'm having issues with the Garmin Express client?
What should I do if I am having problems downloading updates in Garmin Express?
Also, if it is not updating the System Software (Firmware) on the device, you can always try WebUpdater to perform the update. If you use this method, I recommend deleting the device from Garmin Express, performing the update and then adding it back to Garmin Express so the software versions are updated and current in the application.
How do I update the software for my Garmin device?
If this does not resolve the communication issues either to or from your device, it would be best to contact Product Support by phone for in depth troubleshooting.