Maybe double check the access rights for the recycle bin in the admin area?
So... I've seen this before as well, and I know I fixed it, but I exactly can't remember how.
As Scott mentioned, you first have to set access rights on the Recycle Bin.
Here's the support ticket: https://support.episerver.com/hc/en-us/articles/115004100463-Episerver-recycle-bin-trash-appears-to-be-blank
Let me know if that doesn't work, as I might have another idea if that's not it.
A client has reported that deleted content does not appear in the recycle bin however if they search for it they can then locate it using the search in the trash.
I'm guessing that by deafult it only includes a certain amount of items when it loads and the items they are expecting to see are not there due to the number of deleted items exceeding this default amount. Searching is focusing the results so that the items they are expecting are included.
Has anyone else experienced this before and managed to resolve it?