I do have the very same issue with Ryzen 2200G on an MSI B350M. HDMI works during boot up (BIOS) but as soon as Win10 with installed AMD graphics driver (18.5.1) starts HDMI does no longer work, I need to use DVI then (with 1920x1080 only since this is the max for DVI with 2200G).
Without installed AMD driver, i.e. with standard Windows graphics driver HMDI works under Windows!
See also my post in MSI forum: No HDMI output under Win10 (64) with MSI B350M PRO-VDH and Ryzen 3 2200G
I found a solution by doing the following:
- Make sure you do not have any AMD driver installed by running the AMD deinstallation tool.
- Install the driver version published by MSI (AMD Chipset Driver V17.40.3735 for Raven Ridge in my case), download and install it manually not automatically with LiveUpdate
- Now you can upgrade to the original AMD graphic driver (V18.5.1 in my case)