I fixed it by choosing the standard content of the windows on start up again.
I don't know the exact english translation, but it is the 9th option in the settings.

Anybody have a fix yet for the Access Denied error message when opening the app? It has been happening on my OnePlus 3 for weeks and it's very annoying. I've tried uninstall and cache clear but nothing works. My phone is not rooted and I'm on the latest Nougat version of Oxygen OS.

Echo what others are saying.
Moto z force Android 7

Same problem. Led me here. Seems like a bug: Have tried turning on and off different Solid Explorer settings, without success. Problem: Every time SE is started, I get an "Access Denied" message immediately (bottom of the screen). Everything does seem to work fine, but I want to stop the message from popping up every time. This has been occurring for weeks.

Solid Explorer 2.2.5 - Build 170107.N.1
Android 7.0.1 - Nexus 6

Same here, just started with 2.2.4 161210.M.2

On a Nexus 6P 7.1.1, enrolled in the beta program

Same here, just started doing it yesterday I think.

Me too, nexus 5x, android 7.1.1.