Plugin not found in older macOS

I released a plugin (KVR DC entry TinyQ) which seems to not load on older macOS versions. I built using the SDK included in the XCode I use (XCode 8.2.1, SDK 10.12) and set the deployment macOS version to 10.7.
I can load the plugin on the build machine but neither on a 10.10 nor 10.7 machine. Is there anything else I might have overlooked?
On 10.7 nothing (AU/VST/VST3) is found at all in Reaper. I can “load” the AudioUnit on 10.10 but it is shown in red and can’t be opened.

I’m sure this question has been asked several times before but the search only found rather old threads which seemed outdated. Apologies if I missed a relevant thread.

Edit: OK, it seems like I only thought to have set the deployment target correctly to 10.7. I’ll try with the correct deployment target version and get back.
Edit 2: Setting the deployment target to 10.7 makes the plugin work in 10.10 but still not in 10.7. Could this have something to do with the used C++ version (C++14)?

Are you using the juce_video module in your plugin? It depends on the AVKit framework, which is only available on macOS 10.9+.

Thanks, that was the problem.