With the Trash folder open, long-press the e-mail until you see the green checkmark to the left of the message. Then click More in the upper right-hand corner, then tap Move. You'll then get a pop-up list of places to move the message to (such as the Inbox); tap your choice.
Odd; when you select the message, see the green check mark, and tap More, you should see options to Move, Register as spam, Add star, or Mark as unread. I don't know if an app or system cache clear would make a difference, but it wouldn't hurt to try them. AFAIK the app hasn't received any updates.
Do you have the phone in Easy mode? If so, you might try putting it in Standard mode, i.e., Settings > Easy Mode > Standard Mode > Done