Sorry, I just tried building on another machine and am not having the issue, so I think my problem must have been a package I had on dev, even though I thought I had freed all of the JuMP dependencies. If it’s a common issue I have when developing multiple packages I’ll post back here with how to resolve. Thanks.
Update: Ok, in case this is helpful to anyone else, I think I have figured out something that has been causing me a great deal of confusion with the new package manager and which I think was causing this issue. With the new package manager, if you have a package in dev, once you do a pull you still need to do dev PackageName in the package manager again, otherwise Pkg will not update its metadata.