Veracrypt has back-up headers located elsewhere in the volume that are unlikely to have been overwritten.

First thing's first I would strongly recommend copying the drive as it currently exists bit for bit to another drive of equal or larger size. Don't work on the original if you can help it.

Now with this copy, you should try to check the option to use the backup header when mounting and try again. If the partition is gone and veracrypt doesn't see it you'll need to try using something that recovers partitions and doesn't mind encrypted partitions or partitions or file system types it doesn't understand and use that to ON THE COPY recover and recreate the partition (this will write data and can cause the possibility of further loss or worsen your ability to recover which is why it is important to perform it on a copy). Testdesk may work for this but there are other options that probably are better.

See this list: https://old.reddit.com/r/datarecovery/wiki/software and choose something from there if this data is truly important. Again only work on a copy on another drive. Some of these software examples actually work against the original drive and make a copy elsewhere and should be safe to use on the original drive so long as they have you select a target drive to push the recovered data to but read the documentation. Testdisk absolutely must be used on a copy.

You will incur data loss and likely should run one of the file recovery software mentioned on the drive once successfully mounted in veracrypt to attempt to recover as much as possible.