Experienced an issue where the mouseover was not working on a specific character. After enabling script errors it called an error on line 235 of the ElvUI_MythicPlusDatatext.lua file. After looking at the lua file, the offending piece of code is a duplication of an array variable on line 235.

Code contains the following variable call: "affixInfoaffixInfo.level"
which should be updated to: "affixInfo.level"

After fixing this line the mouseover was working properly

This will be fixed in latest release.