Check Payment processor is not working for CIVIEVENT
If you need the payment through "Cheque" you don't need to enable payment processor -

All you need is to enable "is pay later" option in your event config page - Payment processor are used only when you do online payment using credit or debit cards.

So, disable your payment processor and select "is pay later" option and then give a try - that should work correctly  

Refer: https://docs.civicrm.org/user/en/latest/events/creating-an-event/

I guess this helps !!!