Messages from the compiler are very common and should not be treated as errors with the Traffic Global program. Many default airports in FSX/Prepar3D do not have enough parking spaces to accommodate real-life levels of AI traffic so you may see multiple indications of free parking spaces not being available if you haven’t replaced the airport with custom scenery or enhanced the airport with modified parking spaces.
Other errors explained...
"XXXX" is not a recognized airport identifier
Some airports in the AI schedules do not exist by default in flight sim (China has multiple new airports that are not accounted for, for example) but these have been left in the database for those users who have added third party versions of these airports to flight sim.
Unable to find available parking at XXX for <aircraft name>
This error indicates that the airport at which the compiler is attempting to create AI flights cannot find a suitable parking space for the aircraft type. This could be because the airport does not have enough AI parking spaces to handle real-life levels of traffic (a common problem with default airports) or that the correct type of parking space is not available (no spaces big enough to accommodate an A380, for example).