If you're having difficulty when signing up for a comp series, warning you about conflicting mods, chances are you downloaded a series mod from a server or installed an rfcmp skin pack which can mess with version number. OR in my case, you have a mod track installed which messes up another track's version number. You see, i have ISR Daytona mod installed. (I'm not gonna link it, please google it if you want it) And that daytona mod, while good, creates an empty, second version of a random it track it chooses and that second version created, always has the same version number as daytona mod. For me, the victim was circuit d'azur. My installed daytona is v 1.28. So it created an empty version of circuit d'azur with a version number of 1.28 (i say it's empty because it really is. There's no track map or km info when you expand the secondary version of the victim track.) TL;DR If a comp says "conflicting mods" when you try to sign up and you're sure you have no league mods or skinpacks installed, chances are it's a mod track. Check for them.
brianza oval addon also changes original brianza's version, if you cant sign in classics series this is probably the reason