When using a browser, connect to PExx08 series PDU can not login the error message is Login fail.  

Upgrade PExx08 firmware to  V2.4.239 or later to can solve this issue.  And please adopt the attached WEB broswer to do so. (Firefox Portable V.107.0) 

You can also download for below web site:

https://sourceforge.net/projects/portableapps/files/Mozilla%20Firefox%2C%20Portable%20Ed./Mozilla%20Firefox%2C%20Portable%20Edition%20107.0/

To upgrade the firmware, please download the firmware and manual from 

https://www.aten.com/global/en/supportcenter/downloads/?q=PE6208

Please check the manual for how to upgrade firmware. 

If you still have problems, please contact ATEN Tech Support

https://eservice.aten.com/eServiceCx/Common/FAQ/askQuestion.do?type=None