After asking on the FSUIPC forum I was told this is an ADE issue.
I have read the thread you recently started on this issue in the FSUIPC version 6 Main Support Forum ...at:
https://forum.simflight.com/topic/99773-fsuipc6-will-not-connect/
John Dowson has kindly offered to look into providing a test version of FSUIPC version 6 which 'may'- or 'may not' work with ADE in its current build.
I believe you should know that ADE was tested only with earlier builds of P3D version 5, and IIRC, ADE may not have been tested with P3D version 6.
So, John Dowson has AFAIK correctly assessed the situation.
We may- or may not- not see a reply to this troubleshooting scenario by ADE author Jon Masterson (aka "scruffyduck"), but I hope we do.
I believe we should test ASAP, any version of FSUIPC version 6 John Dowson offers, to extend use of ADE for Prepar3D version 6 and later updates.
I do not know how extensive of a FSUIPC feature set ADE requires and/or uses when it runs as a 32-Bit (aka "x86") executable with 32-Bit DLLs.
AFAIK, if all ADE requires / uses to communicate via FSUIPC version 6 with P3Dv6 is the same as for P3Dv4, then ADE is fully functional in P3Dv4.
Based on my limited knowledge of programming, this seems feasible to implement, and should be pursued to extend the prospective use of ADE.
I am able to use FSUIPC version 6 and ADE 32-Bit with P3Dv4.x.
I am also still able to use a FS utility written years ago in VB6 to read / write certain FS variables via FSUIPC offsets via FSUIPC versions 3, 4, 5, 6, 7.
So, I recommend the OP of this thread to request that John Dowson proceed with his very kind offer to release a "test" build of FSUIPC version 6.
If John is amenable to this, I am confident other FSDEV forum participants would also be willing to test that FSUIPC build and offer feedback.
Thanks for following up on this, as it may help extend use of ADE as a valuable FS development resource for current- and future- Prepar3D users.
GaryGB