This kind of problems are very common. Sometimes the server gets stuck and as a result the payment is rejected which means that the money you have paid will get returned to your account automatically. This happens for most of the cases and you have to wait for 2-3 official days. If not updated or the amount is not refunded contact your bank first enquire about it and if they won't be able to say any faults contact MHT CET.

For the MHT CET contact details visit the link below:

https://info.mahacet.org/mahacet/contact.html

To know more about MHT CET visit the link below:

https://engineering.careers360.com/articles/mht-cet

I hope this answer helps. All the very best for your future endeavors!