I upgraded a bunch of 10.2 desktop to 10.6 without problems.
I had only one 10.1. with a License Manager with the same version not licensed and not being used.
I uninstalled the license manager 10.1.
I almost sure that 10.1 is included in the target system but maybe I am wrong.
but when I started the installation I was prompted to uninstall the 10.1 in order to continue.
I didn't do it: I upgraded from 10.1 to 10.4.1 and then to 10.6. --- > OK
Do you think something was left behind from license manager?
Why the installation was detecting the 10.1 as a problem
in System32 there was no Normal.mxt
I know it is supposed to be in appdata/esri/roaming/destop10.x/arcmap
In Desktop10.6 there was only Catalog and the addInFolderList . Nothing else.
I could save the mxd but still, after I opened again a new mxd I got this at closing?
The normal.mxt was not created at all.
(I checked the 10.1 folder and all the default folders were there as it should be.)