VERIFIED SOLUTION i

Resolve issue where WMS shows a black background using PNG (32bit images) in MapInfo Pro

Product Feature: Web Services/EOLS
Product: MapInfo Pro, MapInfo Professional (all versions)

Issue

Some WMS services show up in MapInfo Pro with a black background map. This black color can be set to be the transparent color but this also cause missing information because also black map content is not displayed any longer.

Cause

MIPro does not natively support 32-bpp. It converts it to 24 bpp. 
It appears that the background transparent color got lost during this conversion from 32 to 24 bits. 

As soon as the image is loaded in MapInfo Pro it can be found in the session folder under %temp%\MIPRO. Right clicking the PNG image stored there discovers if it is 32 bit.  

Resolution

UPDATED: September 11, 2017
There is no solution available yet.

As a workaround other image formats can be used as a server usually does not just provide one image format. But it can have the same issue as PNG.