Can't seem to empty trash

After getting messages saying I’m running out of space on my account, I cleared out a load of old emails, and now have 1750ish in trash. However, no matter what I try I can’t seem to empty the trash.

I’m using Firefox on pc, Linux netbook, and Android phone. Tried clicking “empty trash” from the tree, and going to the folder and selecting all. Also, they don’t appear to get deleted automatically after 30 days, even though I have that option ticked.

Is anyone else experiencing this??