Thank you for contacting Square Enix Customer Support. We hope all is well with you.
We appreciate your time reaching out to us regarding i2501 error. We will be glad to assist.
We apologize for any inconvenience you have experienced with our authentication systems. The i2501 error is an error that is triggered by the system to protect accounts. Many actions can trigger this error, such as a slow internet connection, use of a VPN or an odd connection (EG: schools or cafes), a possible virus detected on the device, many rapid payments at once, and numerous other actions.
Additionally, we have provided a troubleshooting guide for you if the above actions do not apply and you are still receiving the i2501 error. We advise clearing the cache/cookies/browsing data from your default web browser, disabling any web browser extensions (EG: ad-blocker), switching to Microsoft Edge and trying again. You may also try using a smartphone running on a mobile data connection (WiFi disabled). We also suggest resetting the connection (router/modem) you are using to connect to the Internet and waiting a full 24 hours since your last attempt before trying again.
Please check to see if any of the listed actions apply to your situation before attempting to access our services again.