How can I solve this PCB problem in Altium?
Altium has a feature called &quot;Rooms&quot; that allows you to define zones on your board when you want certain components to be (or not). If you don't know it is active, then you'll get the error message shown in your screenshot:

Solution if you don't want to use that feature:
Project properties &gt; Class generation &gt; uncheck &quot;create room&quot;.
Go to rules, search Room, delete rule for Room definition.
Also delete the Room.