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I am not from Laminar Research; just a flight simmer from down under.
I am of the opinion that you have 2 issues.
Issue 1. Trying to use XP10 aircraft within XP11. It is a known fact that some XP10 aircraft will not work within XP11 as it is a totally different package. You could try loading your XP10 aircraft into XP11 version of Planemaker (supplied with X-Plane software) and then "save as" an X-plane 11 version.
In addition you should also watch the following YouTube video at https://www.youtube.com/watch?v=V4RjIxrhkXs Consider the message about version types rather than where to place the aircraft in the X-Plane file structure.
Issue 2. Trying to use X-Plane 11 with the the latest version of the Mac OS. In your case "Catalina". Laminar Research was/is fully aware of a known problem between XP11 and your current OS when XP11 version 40 was being tested in the Beta format.. Just after XP11.40 Beta 11 was released Laminar released version XP11.40rc1 for public use. I am not aware if the " matching" problem has been fixed. You may chose to upgrade to this version in anticipation that the problem has been fixed.
If it has not been fixed then watch the following YouTube videos involving Austin Meyer the creator of X-Plane. He was and to the best of my knowledge is still involved with the XP11.40 version development. and I suggest you make direct contact with him to ascertain is the mismatch has been fixed.. His contact details are provided in the following links at https://www.youtube.com/watch?v=v4UfGE-JJY4 and also at https://www.youtube.com/watch?v=WROEk_Jv33w
Good luck in solving your problems.
You may chose to upgrade to this version in anticipation that
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