Our Access Control Plugin is compiled for Milestone SDK 2019 R1. Can that plugin be used on a 2020 R3 Milestone server?
Any extra details would be appreciated.
Yes, it should be possible, but the recommendation is to use newest SDK, you should be able to read all about it in this knowledge base article - https://developer.milestonesys.com/s/article/about-MIP-SDK-compatibility-with-XProtect-product-versions