Problem adding Multiterm to Passolo 2018

I am trying to add a local Termbase to Passolo 2018 (version, when I click "browse" I receive the following error:

"The selected Term Information Provider returned the following error: Could not load the file or assembly 'log4net, Version=, Culture=neutral, PublicKeyToken=1b44e1d426115821' or one of its dependencies. The system cannot find the file specified"

So far I have received 2 help suggestions:
1. Copy the file "log4net.dll" from the location C:\Program Files (x86)\SDL\SDL MultiTerm\MultiTerm15 to C:\Program Files (x86)\Common Files\SDL\MultiTerm15
2. In Passolo > Tools > Addins > Translation change the SDL Trados Studio addin Load Type to Load on Startup and restart Passolo

The mentioned file was already in the suggested location, and the second option did not change anything.
Further suggestions and solutions are welcome.