Unable to upload to EX2 via Mycloud app or website

PC: WIndows 7 pro
Device: EX2
F/W: 2.11.176
Browsers: IE11, Firefox, Chrome

Suddenly started to be unable to upload files to my EX2 when out of the office

When out of the office I can connect and navigate the User interface, open and download files. However if I wish to upload from my Laptop to the EX2 I get a File Failed to upload error with no other info.

I can use either method if I’m actually in the Office on the same network and successfully upload file to the EX2.

The drive is healthy and up to date.

There have been no changes to the Router configuration that I am aware of.

Any suggested fixes or extra troubleshooting I could do?

Thanks in anticipation!

Richard