I am using OKpay.com payment module in my billing system WHMCS.

And this error started appearing on okpay payment page:
"There are no payment methods available for the merchant in this category."

When i asked okpay they said:

Due to ongoing upgrade of OKPAY, most services are not available at the moment. Our managers are doing their best to restore all functions ASAP.

So far we kindly ask to proceed with your verification procedure as we have new requirements for the documents set by Mayzus Financial Services. Once all documents are uploaded, please create verification request and our support managers will check it. If you want to accept payments, you need to open a corporate account and provide documents either for your company,or your sole proprietorship.
Do not hesitate contacting us again should you have more questions or problems.
When trying to send out a few USD to other OKpay user, it says "You have exceeded your monthly operations limit. If you want to increase your limits, please verify your account." and i last sent or withdrawn money before months!