Playing Apple TV+ content is allow on a limited number of devices per subscription for simultaneous use. That includes Family Sharing (i.e. devices from other users in your group). Other Apple TV app Channels may have other limits. Other streaming services may also have other limits. Rented movies allow one device for streaming and one device for download (offline use).
Download and stream shows, movies, and events from Apple TV+, MLS Season Pass, and Apple TV channels - Apple Support
Downloaded content from the iTunes Store and other media though Apple services require an “authorized” computer or “associated” mobile device. Those have limits too. That is separate from online streaming, though.
Authorize or deauthorize your computer for iTunes Store purchases - Apple Support
View and remove your devices that are associated with Apple ID purchases - Apple Support
So what content were you trying to stream? From Apple TV+?
Have you tried quitting the TV app on other devices where you were signed in, and have you tried signing out of forgotten/overlooked devices that you are not using anymore/at this time? Check your Apple ID device list to find where you're signed in - Apple Support