gio trash has stopped working for me

Issue

If I open a terminal and type:

gio trash ~/trashtest/test.txt

The file test.txt is moved to Trash (i.e. ~/.local/share/Trash/files, or trash:///) successfully. However, if I try:

gio trash ~/trashtest/

I receive the error:

gio: file:///home/**myusername**/test: Trash portal failed on /home/**myusername**/test

I use Nemo on Cinnamon and I believe that it uses the same backend as gio trash to delete files - when I attempt to move a file or group of files to Trash, it works, but if I select a directory and use 'move to Trash', I get an error dialogue box with the same error: "Trash portal failed on chosen-directory-path"

This is on an Arch-based system where I have a / partition and a /home partition. To the best of my knowledge there are no symlinks or network mounts involved, only a separate partition on the same hard drive monuted at /home. I can confirm that the directories I've tested this on have had 'myusername:myusername' in terms of ownership and group, as does the ~/.local/share/Trash directory and all subdirectories. I have also tried running gksu nemo to use Nemo with elevated privileges, and the same error occurs, even when creating an empty folder in /root and then attempting to move it to Trash.

I have installed and tested the trash-cli utility and attempted to move some of the same directories to Trash using trash-cli, and it works without issues.

Moving a folder into ~/.local/share/Trash/files works, and if I then run gio list trash:// the folder appears in the output.

Summary

gio trash fails with an error if I try to trash any directory, but trashing any file(s) still work perfectly.