Product 0 does not support upgrading from version 16.0.864
I'm getting the same issue... I read that I needed the July SP installed.. did that
Same error .. then I installed the March 2020 SP MicrosoftDynamicsGP18-KB4536496-ENU .. same error
Originally I had installed the Dec 2020 SP c/w tax table updates ... but after reading this I uninstalled and started over
Doesn't seem to matter what SP I find for GP 2018 it doesn't want me to upgrade.
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Originally I appended an older version of this topic but it showed as verified and answered so I wanted my upgrade issue brought forward as this is a newer version of 2016 that I'm working on.