I'm sorry this is happening, I know it is really frustrating, particularly when it's coming out of your own pocket However, these forums are not exactly run by Tableau Support, they are really meant for the community of volunteers around the world (e.g. you & I) to help each other regarding the actual products (Desktop, Server, Prep, etc.) so these exams really don't fall into this category. It's best to work with the exam team on this and provide the feedback so they can improve the process.
At least you know you need to follow the minimum hardware requirements and will be better prepared for the exam. Good luck with it and I hope you pass, we can always use more experts like you to help out the community
It's unfortunate to know. I am also planing to take the exam in a couple of weeks. I read somewhere, even if Virtual Machine doesn't work, the exam will not be renewed and we need to attend the test by paying $250 again.
For your information; As per the Tableau policy, we can attempt to the certification two times without any waiting time. After 2 times there will be waiting period of 2 months.
Please plan your exam accordingly and all the very best and you will pass the exam .