A very small number of customers with Apple Watch Series 5 or Apple Watch SE models running watchOS 7.2 or 7.3 have experienced an issue with their watch not charging after it enters Power Reserve.
What to do if your Apple Watch exhibits this issue
To check if your Apple Watch is affected by this issue, place your watch on the charger that you normally use, then wait at least 30 minutes.
If your Apple Watch still won't charge, contact Apple Support to set up a mail-in repair free of charge. Your watch will be examined before service to verify that it's eligible for free repair.
Apple just released watchOS 7.3.1 to resolve this issue for devices not yet affected. Notably, Apple recently announced a similar battery replacement program for 2016 and 2017 MacBook Pros that don't charge past 1%.
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