Two solutions are given on page 5 of the quick start manual (Tnx John AE5X). You can download it to read here: https://physics.princeton.edu/pulsar/k1jt/Quick_Start_WSJT-X_2.0.pdf
The article suggests to download and install a open SSL library. However, in my case and a few others this doesn't work at all. The easiest step, and till now it worked for many, is downloading this file: https://lotw.arrl.org/lotw-user-activity.csv and move it to the WSJT-X log directory. This directory can be opened from within WSJT-X -> File -> Open log directory