The new Archers update is not possible to launch. It won't launch with any version of Spell Engine and SimplySkills.

(With 14.3 installed)

(With 15.0 installed, and also with 15+)

The error literally says what needs to be done.
Simply Skills needs to be updated or disabled.

So you're saying you no longer support simplyskills? It's the latest version. There is no update.