'This may take a few moments' message being immediately followed by 'Disconnected from server' message. Other invited players (some over the same internet/wifi connection) can login and play with no issues or error messages. As owner of Realm, I could make changes to Realm (switch between creative/survival; invite new players) but attempts to connect to server to play resulted in this error every time.

After several days of failed attempts (same error message each time), I created a second xbox live account and using the primary account invited the secondary account. Secondary account worked just fine for several days then same issue reoccurred with the secondary account.

Both issues seemed to start after using a potion (specifically swiftness, though I believe the issue may be related to potions/status effects in general) and being disconnected from server while potion is in effect (error message for being disconnected was 'Disconnected from server'). After being disconnected, all subsequent attempts to log back in to server to play are met with 'This may take a few moments' being immediately followed by 'Disconnected from server' message.

Using the primary account, I uninvited secondary account. Then re-invited secondary account. Did not resolve error for secondary account.

Changing Realm type from survival to creative and back did not resolve error for primary account.

Uninstalling application and reinstalling application did not resolve error for primary account.

Primary account continues to have error.