Can you download the version of the app that worked from a different app store?
ApkPure, UpToDown, and a few others will allow this.
The new version of the app will need to be uninstalled first.
I had the same problem with the app a while back, and I resorted to just using a browser to get onto Pluto TV.
After I uninstalled Pluto TV, cleared the cache of Google Play Store and Google Play Services, I reinstalled Pluto TV and it works fine now.