Can you check that you are not using the master branch of MultivariatePolynomials but rather the latest release ?
This is due to the breaking change in Reverse monomial order by blegat · Pull Request #225 · JuliaAlgebra/MultivariatePolynomials.jl · GitHub which needs Update with MultivariatePolynomials#bl/term by blegat · Pull Request #113 · JuliaAlgebra/DynamicPolynomials.jl · GitHub.
If you use the latest release of both packages, everything should be fine.
I am waiting to be done with all the breaking changes I need to do for gcd performance · Issue #194 · JuliaAlgebra/MultivariatePolynomials.jl · GitHub before making new releases. In the meantime, it’s best to stay way from the development branches and stay with releases.