I experience the very same case even if the WiiM Amp is already on when I select it as audio destinationMy case is slightly different and it is with the WiiM Pro Plus but the behavior is similar. And yes if I use the play button on the WiiM Remote to power on the WiiM Pro Plus instead of the on/off button the music plays.
Details of my situation are here:
Optical in stops working after stand by mode.
Hello, after WiiM pro plus have been in stand by mode and you turn it on, optical in is not working from TV (Pretty new Phillips ambilight TV, 2021) Tried a lot of things, secured that Phillips TV optical out only send 2 channel stereo, turned of atmos, dts, Dolby etc. Tried change Apple TV with...forum.wiimhome.com