Zelle is returning to service after an outage for customers at some banks due to what the popular peer-to-peer payment platform blamed on a problem at a different firm.

DownDetector, which lets users track outages, showed a spike in customers reporting payment problems starting Friday morning before starting to fall a bit in the afternoon.

A Zelle spokesperson confirmed the trouble in a statement to CNN and said that the problem involved payments giant Fiserv, which provides services to some banks.

“Earlier today, we experienced an internal issue that temporarily disrupted service,” a Fiserv spokesman told CNN. “The issue has since been resolved, and we are now working to process the backlog.”

Fiserv said the outage was not a result of malicious activity, and it is working to prevent a similar problem in the future.

Zelle’s spokesperson said the payment service was working with its partners to resolve the matter.

“Zelle users may see transactions marked as ‘payment pending’ in the meantime,” the spokesperson said.

Zelle did not say which particular banks are impacted. However, DownDetector users from Truist and Navy Federal Credit Union reported issues.

One Truist customer complained on DownDetector that their rent payment has been pending since Thursday evening.

“I feel like my money is just floating and no one will help with anything or take any accountability!” the user said.

Representatives for multiple banks referred CNN to Zelle.

Bank of America spokesperson Matthew Card confirmed that some customers were having Zelle trouble.

“Earlier today some clients experienced a delay in sending and receiving certain payments,” Card told CNN. “This was a vendor-related issue that affected multiple banks. The issue has been resolved.”

American use Zelle to instantly zip billions of dollars a day to each other.

Zelle is owned by Early Warning Services (EWS), which is co-owned by big banks including JPMorgan Chase, Bank of America and Wells Fargo.