We may have already resolved this issue but I'll post this in here anyway in case others run into the same error.
After 3 months of not using Workforce (due to COVID lockdown) some of our mobile workers ran into an "untrusted host" error when they opened assignments on Workforce. This was specifically with Android, and specifically with the Note 8.
The users could open the app and view their To-Do list, but when they clicked on an individual assignment, they got this error (below) and couldn't click the "trust" option. They had to close the app and re-open it for every single assignment in order for it to work.
We advised the users to delete the app & reinstall it, and now it appears to be working fine under version 17.0.1 and Build 1914.
I can update if this happens again, but just figured I'd post in case others run into this issue in the future.