No mod and no buttons.

What do you mean?

(Google translation from Russian)
Hello!
I have a similar situation: the mod is in the “mods” folder, but when loading the game it does not load: there are also no buttons in the menu and when loading, the OpenEye mod is not requested to load.
I enclose the client download log file.
latest.log

And on another assembly, for tests, there are no problems with the mod!
latest.log

Hope this helps!
Good luck

And is this information necessary to transmit to the developer of the Malisis mod or is this done automatically?

This is caused by MalisisCore bundling an old Mixin version: Ordinastie/MalisisCore#172

As a workaround, you can try to rename either the ReplayMod jar to start with a (areplaymod-1.12.2-2.3.0-b1.jar) or the MalisisCore jar to start with z (zmalisiscore-1.12.2-6.5.1.jar), either way the ReplayMod jar (and therefore its more up-to-date Mixin lib) should be loaded before MalisisCore.

@SeagalKru The issue I linked to is the same thing except with VanillaFix instead of ReplayMod, so they should already be aware.

Hmm ... Well, good. Then we will wait for the fixes! ;)