There are some possible answers:

• You may have unresolved issues in your log. To fix this, go back to your game and open the log on the bottom right corner. You will see there what you need to do to resolve the issues.
• You may be experiencing network errors. Make sure that whenever you create a game, you have a stable internet connection.
• You may have typed too many characters either in the game's name or description. Please know that emojis count as multiple characters.
• Your game's name and/or description might be empty. Make sure to write something on those fields!