Azure AI speech studio - synthesis failed

Hi,

in my TTS project all files created so far cause a failure when I hit the Play button. I get following error msg:

Response status code does not indicate success: 400 (Synthesis failed. StatusCode: FailedPrecondition, Details: '=' is an unexpected token. The expected token is ';'. Line 1, position 535..). Connection ID: c2e319c0-c447-11ef-8937-33bd13f92760

Changing voices does not solve it. Location of the speech service is "Germany West Central"