TempVoice sends you a notification when there was an error creating a temporary channel. Make sure you have DMs enabled and didn't blocked TempVoice.
Ratelimit
Most Discord servers have a limit of 2,000 channel creations per 24 hours, which applies to all bots. Once this global limit has been reached, no bot can create any more channels until the limit is reset. This limitation is imposed by Discord and we cannot prevent or increase it.
Very active communities should not rely entirely on temporary channels. Provide enough casual voice channels at the top of your server as a first choice so that users might prefer not to use a temporary channel for a quick call.
As this limit applies to all bots, it is advisable to avoid using bots that create channels, such as ticket bots. As an alternative, you can use forum channels or modmail bots.
It's also recommended to lock temporary channel creation behind a role with some requirements (level, time, etc).
This can help prevent your community from reaching the total limit for creating channels.
Check for missing permissions
Reinvite TempVoice to quickly refresh all permissions: