Apple has reported that a limited number of users of Apple Watch Series 5 and Apple Watch SE have experienced a problem which prevents them from charging after entering Power Reserve mode. Recently, watchOS 7.3.1 has been created as a remedy to the problem. However, a free patch is provided to those who cannot upgrade and are still faced with the bug.
“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,
mentioned by apple in a recently popped in support page
You can search the Apple Watch watchOS Update by going to the Watch app for the iPhone or by tapping General > About in the Settings application on your Apple Watch.
The Apple Watch Series 5 was launched in 2019 with the iPhone 11, while the Apple Watch SE was released last year with the iPhone 12. You can email Apple Help to have the fix completed for free. This is required as a mail-in repair in qualifying markets. If the product is suitable for maintenance, then the repair will be free. If you do not have any of the listed problems, then upgrade to the new version of watchOS ASAP to avoid any issues in the future. It doesn’t appear to impact other Apple Watch versions, but it is better to upgrade to watchOS 7.3.1 to have all the new bug patches and protection improvements. If you are trapped, contacting Apple Help is a successful idea.