Woocommerce checkout error

Hi,

I have custom payment gateway plugin and it use bank redirect form as payment metod. And my problem is with Woocommerce checkout, after going from my cart to bank page everything is ok then customer gets back to site to confirm order i get this message: ”
Security error. Unauthorized access detected.” The transaction is recorded on the bank’s system and I get the money but not on my wordpress system it says order failed. Bank have success url where i put https://www.mywebsite.com/checkout/order-received/. I tried to turn off my cpanel ModSecurity and tried Simple SSL plugin (some says problem with https:) and problem is the same.My site have https certificate.

MY PAGE-BANK PAGE-BACK TO MY PAGE
My checkout page everything is ok then redirect to bank page everything is ok, customer enters credit cards info and payment is successful (the amount gets charged on credit card) and it redirect back to my site where I get error “Security error. Unauthorized access detected.” and in my orders it says order failed.

Thanks.