Hi Kevin,
A support moderator in Microsoft Credentials forum can help fix whatever issue is preventing you from scheduling exam. To contact them, please ask your question using link below. They will respond to your question within 2 business days typically:
https://trainingsupport.microsoft.com/en-us/newthread?threadtype=Questions&forum=mcp
Please click Accept Answer and upvote if above was helpful.
Thanks.
-TP