How can I run server's function (in BP)

I’m doing a multiplayer game. There is 2 characters. Server and client. Client shots remote bomb, run away and then detonate it.

Then character’s Blueprint function “DetonateRemoteBomb” is being called. It’s a local function (I mean it don’t need to be replicated), that function finds object of that bomb in the HUD’s array (Array is in HUD blueprint, because when bomb is spawned, the index of this bomb begin indicate about it above the mesh. And to draw this index the HUD should know, what the object he’s indicating. So, object of the bomb is put into HUD’s array), then character executes function “start boom” in this bomb. The function also don’t replicated.

Then, the function executes another bomb’s function “Server Boom” with flag “Run on Server”. And this function doesn’t work.

Any function at all that I flag with “Run on Server” will not work anymore. But in the character’s blueprint all this stuff (I mean “RunOnServer” functions) works well.
Why does it occurs?