Summary: For some Situations F1 works good for some it works not good (only opening Help window, which is at least were you can then search on your own).
If you descripe us your Position were you Pressed F1 and what was marked, we can check if we will get the same result. In addition we may help you with the correct info from the Help, as soon we know what you are searching for.
In this case it should work. So page in AS help with documentation of CPU should be opened. Do you have older version of AS installed? Does it work with older one?
I made a fresh upgrade (reinstall) from AS4.12.5 to AS4.12.6
In both Versions it worked for me in this use Case (F1 on selected PLC in System Designer). Here is the upcoming Page GUID: e1ed6868-a63f-4b2f-a8ad-a21234346e6d
It looks realy as an issue on your System.
I would still suggest to use manual Search.
If you need a fix i think you should involve local B&R Support. There will be a deeper analysis of you system needed i think. The start of the analysis is to get more Data of behaviour, as Jaroslav suggested.
Thanks for sharing the solution with us. I think i have to make a posted on my wall with “PC specific → Ask User-Rights” i think we will get such topics more often in days where not everyone will get admin rights as in past days.
Can you mark your post as a solution, so the Topic gets marked as solved.