I can’t add a user as a friend on Monopoly GO!

Some users have reported that the friend addition confirmation popup on Monopoly GO does not appear, even though the friend is successfully added to the friends list.
This bug is due to a problem that depends on Monopoly GO! and not on us. 

Please, completely close Monopoly GO! and reopen it.

This often resolves the issue and makes the confirmation popup appear.

In any case, even if the confirmation popup does not appear, the friend has still been successfully added and can be selected from the user selection screen when sending a trade proposal in Monopoly GO!.
Below is an example showing where the newly added friend appears in the Monopoly GO! user selection screen when sending a trade proposal.