From which firmware version did you update? PreSonuns recommends to install v1.9 BEFORE installing a v2 version, so this might solve your problem already.
If not, you have three options. First, you should make a reset of project, scene and patching. This brings the mixer back to factory settings and (should) make the mixer work as normal. Then there are two more options, which will delete a lot or all information in the mixer. If you want to keep settings, store them in UC Surface (computer, tablet) before you do the following resets.
2) The FX Button Reset:
"StudioLive Series III Console - Factory Reset"
https://support.presonus.com/hc/en-us/articles/115001731123-StudioLive-Series-III-Console-Factory-Reset
3) The Home Button Reset:
"StudioLive Series III Console - Reverting to the Factory Firmware Image"
https://support.presonus.com/hc/en-us/articles/115002810486-StudioLive-Series-III-Console-Reverting-to-the-Factory-Firmware-Image
If that does not help, open a ticket with Support and let them do their check.
