yeah... your best bet at this point is probably just uninstall the game, and make sure any leftovers are deleted. check the C:\Program Files\WindowsApps folder. get rid of 100B7A24.oxyna_1.0.7.0_x64__wyfsmff9ynw7j. check the Deleted and Mutable folders too. also check C:\Program Files\ModifiableWindowsApps. i wouldn't worry about registry. ccleaner probably won't help.
you could also delete your SEGA folder through My Documents. it has some potential garbage that will just re-build when needed. you will lose your settings, though. up to you. however, i do notice, on a healthy game install, deleting this folder forces the launcher to make a file check.
after that, be sure you restore any permissions you changed back to default, if Windows hasn't already done this for you.
for good measure... before installing the game, uninstall Gaming Services. this is for Xbox and there seems to be an error going around. uninstall that, restart PC and check the WindowsApps folder and delete the folder(s) for it if you see any. they would directly contain, "Microsoft.GamingServices...". check both Deleted folders and MuteableBackup too. leftovers should be found, and will get re-used if left. (assuming the uninstalled version is the same of the newly installed version) they stay because the uninstall is incomplete due to files being in-use, i tried to delete directly after an uninstall. re-install Gaming Services and reboot PC to ensure services are completely running and then re-install game.
https://www.microsoft.com/en-us/p/gaming-services/9mwpm2cqnlhn?activetab=pivot:overviewtab
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in my case, i also had no issues other then the lobby lag. tried the fix and blammo. lols.
yeah, so what seems to be happening... in order to use the fix you need to change permissions. which causes a huge ruckus in Windows, it doesn't like it. it will eventually catch on and fix the permissions. for me, it was on every 3rd launch attempt. i tried several times and re-downloading the game too. even the slightest change to Security Permissions induced the issue.
my game was getting moved to the MutableBackup folder for repairs, which took eons to do. i am not sure why the base client that downloaded through the launcher is what gets moved for repairs. i am also not sure why any patch/update data is excluded from that move. even after catching this and manually moving the data back to where it should be, the launcher had to re-download 2~3GB worth. and trying to launch the game as-is from MutableBackup made the launcher in Japanese. LOL
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i know that is a wall of text, but good luck!