The same story that I was trying to remember now, it was an app that has a faucet of Bitcoin, Litecoin, and last thing that has a Xapo wallet but the rest I totally forget. I have checked my email address possible name but I wasn't fine and AFAIK, it was associated with my email address but the problem is I didn't even remember what app it is.
The same as the suggestion ETFbitcoin above, if that is an account for sure it is associated with any of your email accounts, just look at the search button and search the possible combination name as you remember. That is if, the site was still working on but usually, it was considering a long-dead site or whatever it is.
Are those sites still active?
If you know what is the name of the site possible it is if they aren't close.
Does anyone have the address of those sites?
It's unknown and how we can determine what service it is.
Is it possible to withdraw from those sites?
If you've owned and have control of the wallet it might be, but if that was on the site's control, there's nothing you can is to determine first if they are still alive.