First check both players' server, co-op unlock and current quest messages. Then compare the host's World Level with the visitor's. A convenient test is to have the higher-level player visit the lower-level player's world, if the game permits it.
First check both players' server, co-op unlock and current quest messages. Then compare the host's World Level with the visitor's. A convenient test is to have the higher-level player visit the lower-level player's world, if the game permits it.
Open Co-Op, search the host’s UID and request entry; the host can approve. If no request is possible, check the host’s world permissions and the quest and World Level restrictions below. (source)
Check in this order
- Unlock co-op. The community wiki lists Adventure Rank 16 and completion of the early Archon Quest Prologue: Act I as requirements. Both players should check their own co-op menu and any on-screen instructions.
- Use the same regional server. Different devices can play together, but characters on different regional servers cannot directly join each other. Check the server on the login screen and your UID; changing servers may show separate progress.
- Compare World Levels. Normally the visitor needs a World Level at least as high as the host's. Published community documentation notes an exception for a World Level 8 visitor joining a World Level 9 host; check the current game prompt for your exact ranks and conditions.
- Read the blocking message. HoYoverse says some quest stages temporarily disable co-op. Open the co-op icon or try joining to see the named quest, then complete the blocking stage. An event or challenge can also temporarily restrict entry.
- Retry after leaving the activity. HoYoverse suggests completing the relevant event portion, leaving its scene or teleporting elsewhere before trying again.
If the message remains after completing the named task, use the in-game Feedback channel. Include the error, relevant quest progress, UID and screenshots, but never share your password. Don't delete an account or switch servers as a first troubleshooting step.
Sources: HoYoverse co-op troubleshooting · Genshin Impact Wiki: Co-Op Mode · HoYoDex world-level exception · HoYoverse support.