Garmin’s instructions seem to suggest that devices will need to be factory reset if a power cycle does not work. Reconfiguring a watch from scratch would be inconvenient, so it might be worth waiting to see if Garmin can issue an update that resolves the issue. If you cannot wait too long, you might just have to go through the hassle.

The latest update for Garmin smartwatches has countless devices stuck in what's known as a boot loop, when the watch boots and crashes and boots and crashes on an endless loop. According to user reports,

Garmin users are reporting that several models of GPS watches are getting stuck in a boot loop. The company hasn’t yet issued an official fix, so you may want to power yours down in the meantime.