The correct credentials are inserted on the checkout screen of the online store, however nothing happens - no error message is received, the screen is just refreshed. In the error reports we can see new reports generated -
Account #0 does not exist. and
You are trying to login with the credentials of the customer that does not belong to this reseller/provider. There is no error message due to the product bug with id #PBA-83771 ("No exception is shown when the user from provider's customer tries to login to reseller's store").
User correct store url/correct user's information.