San Francisco, Feb 16 : Apple has released watchOS 7.3.1 update with a big fix for those using an Apple Watch Series 5 or Apple Watch SE related to Power Reserve. "WatchOS 7.3.1 addresses an issue that prevented some Apple Watch Series 5 and Apple Watch SE devices from charging after entering Power Reserve," the company said in an update on Monday. The watchOS 7.3.1 update?? can be downloaded for free through the dedicated Apple Watch app on the iPhone by going to General and then Software Update. To install the new software, the Apple Watch needs to have at least 50 percent battery, it needs to be placed on a charger, and it needs to be in the range of the iPhone. Apple's previous update, watchOS 7.3, was released on January 26. The updates include the Unity watch face, Time to Walk for Apple Fitness + subscribers, an update to the EKG app and irregular heart rhythm notifications in select countries, and a fix for a Control Center issue. Recently, Apple noted that some Apple Watch Series 5 and SE models running watchOS 7.2 or 7.3 have been stubbornly refusing to charge after being put in Power Reserve mode. Users affected by this issue can now contact Apple Support and organise to mail their Watch to an Apple Repair Centre for a free fix. /IANS