If the network you're on uses an eero wireless router, your eero settings may cause playback with audio but no video on your Roku app. If your eero router is blocking ads or other types of content, this can interfere with playback on Lifetime, as we are an ad-supported app.
Using the eero app, you can set up a profile on on your eero that excludes Roku devices and then apply ad blocking only to that profile that does not include your Roku devices. Once you have done that, reboot your router and then your Roku app should work as expected.
Here are some support articles from eero that explain this further: