I believe, the error message not related to Serilog
specifically, but is rather because of the code/assembly/package specific structure/modifiers etc.
This following seems to work for me most of the time
Solution 1
Tools->Options->ReSharper
It refreshes the cache and/or some other dark magic
Solution 2
You could try clearing the ReSharper cache implicitly
ReSharper->Options->Environment->General
Solution 3
You can also try unloading and then reloading the project.
Solution Explorer->Right Click
Solution 4
As a last resort you can try to delete the solution cache manually
%LOCALAPPDATA%\JetBrains\Transient\ReSharperPlatformVsXX\vXX\SolutionCaches\