The mandative subjunctive uses a bare infinitive (no -s, no auxiliary) in that-clauses after verbs like suggest, insist, demand, recommend and adjectives like essential, vital, necessary. The were-subjunctive appears in hypothetical conditions and after wish / as if.
After verbs like suggest, recommend, insist, demand, require, propose — and adjectives like essential, vital, important, necessary — a formal that-clause uses the bare infinitive (no -s, no was/were, same for all persons).