Unable to connect the World

Thank you for your report!
However, this issue is Incomplete.

Your report does not contain enough information. As such, we're unable to understand or reproduce the problem.
If your ticket does not look like the example given here, then it's likely to be closed as incomplete.

Also, we'd recommend making use of the search feature before writing a new bug report, as it's very likely that the issue has been mentioned already, and you can add a vote and any new information to the main ticket.

If you are trying to connect to a multiplayer world, then this is a duplicate of MCPE-36190.

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