Unfortunately, Roku-side HDCP issues have plagued Roku devices for many years, and they've never bothered to fix it - its perfectly reasonable to switch to a different streamer platform (e.g. FireTV), which arent reported to have HDCP issues at all.
Basically, the troubleshooting is limited to finding out what in the HDCP protocol chain is failing to verify. Can try using another HDMI cable and another HDMI port on your TV. (one of these will usually work on your standard 720/1080 TVs to fix the problem. ). Since you received same message twice with different Roku units, and was working prior, tend to think it may be with TV HDMI port. (Of course, make sure your Roku units are updated to latest 9.4)
If you have tried switching cables and HDMI ports with no success, then you can read here for another way to eliminate this issue if you want to keep your Roku. It basically entails a HDMI splitter. More expensive ones exist for 4k since some convert HDCP protocols to fix certain compatibility errors.