I found a fix. Hopefully others see this and it’ll work for them as well:
The solution was to subscribe to Cam Plus (just for one camera). One by one, select a single problem camera for use with the subscription. Then, restart that camera…wait a couple minutes. Then you’ll see the “Live view unavailable in Alexa App” should be gone and you can use it on both Google and Alexa assistants. Do this for each problem camera.
FYI, when you factory reset a camera, it gives you an option to try a 14-day trial for Cam Plus…I suggest doing that, then cancelling right after. Good luck.