I can not explain poor Paul, but my English is not good enough.
In addition to the previous forum, with almost no addons, I had a trial version with all the addons in another subdirectory. After I had this version now run for several months without any problems, I have the previous forum off and let the new version go online.
Everything works as it should, no problems.
Only this addon is now showing, advance in the test system it ran smoothly, no output.
It is incorporated by php include in the website.
it will run properly.
There is certainly no fault of miniBB! The fault is clearly on my system environment. But I do not just find my mistake, maybe you have a tip.