Galaxy Tab Pro SM-T520 does no longer see wifi networks
It turned out that the problem was the Passpoint setting enabled by the default. You can find it only in Advanced wifi settings. On Samsung tablet, while in Wi-Fi settings, you have to click on vertical ... at the top right corner, then select "Advanced" and there you can disable that Passpoint setting.

It took me a while to find a solution to this problem, so I hope my post may help someone!