Hi – in relation to the article on July 19 2018 – I have just been talking to Microsoft about this . I bought a Surface Go in October 2018 and downloaded Office Mobile – it stopped working after 30 days – so I set about finding out why . I am being bullied by Microsoft purchase a 365 subscription which they insist I need for this feature to work on the Surface Go . I am in NZ and am about to put this in the hands of our consumer watchdog because on the Microsoft web site and the mobile app it says this feature is free for windows 10 machines with screen size less than 10.1 inches . Thought I would let you know because they lied to you as well .
Actually, Microsoft Office Mobile (Word Mobile, Excel Mobile, and PowerPoint Mobile) is still free (editing) for the 10-inch Microsoft Surface Go even without a subscription. I’ve also experienced issues like you before. Sometimes it required a subscription for editing capability, however, it can be fixed by reinstalling those apps.
Please try to uninstall those apps, and reinstall the Office Mobile apps from here: