On servers that have Gameshark installed and enabled, the Gameshark UI flickers for clients. For example, if there's a Pokeloot nearby, the UI will be grey and say "searching..." for a few seconds, then flash yellow for half a second, with a line drawn towards the Pokeloot, then the line and yellow flash will disappear. This was only tested on a pre-existing server that upgraded from 8.3.0 Pixelmon to 8.3.1 Pixelmon. In singleplayer it seems that the general consensus is that it works. However, someone has reported being unable to open the GUI and someone else (myself) has reported being unable to launch a single-player world with Gameshark enabled, cheats enabled, and on a creative world.

i made a world and opened it to lan for me and my friend to play and we also are having this issue. both of us also tried solo worlds and it does not seem to work for us solo ether.

Hey there!

Thanks so much for the report - there is indeed some issues going on with Gameshark at the moment, so this report will be merged with a preious report, to consolidate all of the related reports. As such, this one will be labeled "duplicate" but will be adressed with the following report:
tracker.php?p=6&t=16606

Thanks again,
Katzyn