5.10 is already very old.
I would recommend upgrading to 5.12.2.X.
https://extremeportal.force.com/ExtrProductDetail?id=01t34000004LenNAAS
As well, As per the 5.12 release notes. The following Browsers have been tested.
Microsoft Internet Explorer 11.0
• Mozilla Firefox 45.0.2
https://documentation.extremenetworks.com/release_notes/ERS_Series/ERS4800/9035512_ERS4800ReleaseNotes_5.12_RN.pdf