From: https://support.wyze.com/hc/en-us/articles/360031490871-How-to-flash-your-Wyze-Cam-firmware-manually
Cams require a Factory Reset prior to power disconnect, insertion of SD w\ Flash .bin, and Flash Procedures. This is listed as required with all new firmware on their Firmware Download Page
I tested this and confirmed that a V3 Factory Reset is a 15-17 second button hold. Firmware Flash on a V3 Cam was also confirmed both backwards to older versions from current and forward from older versions to current versions: After firmware update cameras don't connect anymore - #80 by SlabSlayer