Epic

Yeah we're using a completely different way of Citrix (remote desktop concept) and with that combination there's no problem. I do have to uninstall the old/previous receiver. Maybe it can help other in a near future

For archive purposes, uninstalling Citrix receiver fixed the problem. Not a real solution but after a reboot CCleaner worked again. Somehow my Citrix receiver and CC don't play well together, if I reinstall the Citrix receiver same thing happens again, CC won't work/open at all.

Might be a good idea indeed, will try and see what might come up, thanks for pointing this out.

"FIXED IT" (...well sort of...) -> I was misssing the CCleanerSkipUAC scheduled task Exported this from another computer, imported it in my troubled workstation, restarted and things are doing again as they're supposed too... Weirdest thing is in my opinion is that multiple re-installs did not fix this missing scheduled task edit: BUT only auto.start CCleaner at logon and then I can open it, but when I close CCleaner and then try to re-open, again nothing...really weird... (and after 2nd reboot this also doesn't help though) PS. when I run this service manually I get this errorcode in return: 0xC0000005 (and CCleaner.exe won't open)

nope it's not, like I stated earlier, disabled this (and verified no services or what so ever were running)

Not much to add as what's already stated I'm afraid, CCleaner just won't open... Install, uninstall, re-install is no problem, but when I try to open CCleaner, nothing happens at all. Everything worked fine before Windows 10 update to latest 20H2, I disabled Defender / Microsoft security and Sophos (anti4us) but without result (no solution). The tricky part is that when I start Windows in 'safe mode', there's no problem running CCleaner. But in 'normal mode', nothing happens. I can try other login account or a new account, but with the same outcome, CCleaner just won't start/open. Event logs don't show something weird, except APPCRASH (event 1001), but with no extra info what so ever. Still fiddling with this from time to time, but nothing yet.

I don't have install problems, just still can't open/start CCleaner anymore (disabled anti virus etcetc, as stated earlier)

Just to update current status as is, I have'nt got it pinpoint yet. It will work in safe mode but not in any other way (tried different accounts)... It always worked but now it does not anymore, my best guess is still that something in Win10 does'nt approve ccleaner anymore / at this time

I did reboot more than once, u installed ccleaner, remover all possible reg entries, tried reinstalling ccleaner, ccleaner slim, ccleaner portable but no luck. It just won't open anymore

yeah I know, but there's no solution there... => I'm allowed to install outside the Microsoft Store and i'm not in 'S mode', I disabled defender (as stated earlier) and also tries the CC-slim version...

this does help, now I can open it, but not in my normal account. I still think it has something to do with microsoft defender / security center though. Because when I download ccleaner with edge it does complain about the file and if I whish to keep it anyway, I do think this does prevent ccleaner from opening. I removed Sophos because of testing purposes but that does not make any difference. I do not have problems with any other software so that is why I think Windows is somehow blocking ccleaner. When I try another account on my workstation I do have exactly the same problem, ccleaner will not open.

aaah forgot about that one, yes I'll try...

Also tried slim, same result Can't download that version yet, Windows Update is up to date (at least that is the message it gives me at this moment) Never had these disabled indeed, but for testing purposes I just did, with no result...

I can not open/start ccleaner any more, even tried to update to current realse 5.74 but still nothing. Running Windows 10 x64 Pro -up2date- version 20H2 build 19042.572 (Windows Feauture Experience Pack 120.2212.31.0), even without Windows Defender and Sophos antivirus (both disabled), nothing happens. When I try to open, it seems like it crashes immediately, no ccleaner window or whatever, can't even see the service starting in task manager (it does seem to start for about a second and then it's gone). Tried ccleander.exe /debug & ccleaner64.exe /debug but nothing, but this is expected since ccleaner just won't start at all. I tried looking into eventvwr.msc - windows logs - apps and there I see event 1001 : APPCRASH (but without info), tried uninstall, tried portable, removed ccleaner reg.keys from windows registry, but I cannot seem to fix it :'( and I'm kind off running out of ideas right now. With kind regards