Primitive Mobs do not spawn without a quick fix in the config by adding the number 1 to all of the modded mobs under the spawnbiome entry. After exiting and reloading the world, the mobs no longer spawn until you edit the config again. Otherwise, the two mods are not compatible.

opinionated comment
Please fix this, I love this mod and would love to use these two together with Quark to get a Vanilla+ experience.

This is a real problem. Biome Bundle and Primitive Mobs are a really relevant combination! Both are aiming to improve the Vanilla experience. As a server owner there is no current possibility to fix it! The spawn algorythm of primitivemobs-1.1.6_beta.jar worked at least but is not very stable. I hope you can fix this issue soon!

I really hope this gets fixed too