Many users have reported that they “can't enter the room code.”
This is a display bug in the client:
The room code has actually been entered, but the numbers do not appear in the input field.
Temporary workaround: Enter the 6-digit number as usual in the room code field,
then simply tap “Join”;
If the room has a password, enter the password in the password field first, then tap “Join.”
Patch 1.0.8 will be released shortly.