I upgraded to the latest mekanism and now the universal cables are not connecting to my MFR/Thermal Expansion/Ender IO machines. I am using mekanism 7.1.1.125 ender io 2.2.0.272 MFR 2.8.0RC4 Thermal Expansion 4.0.0B6

I'm using hermetcraft modsause and found that if you put an energy cell in the mek power source it will charge and use that to power your machines before you can get different cable. I was using a windmill and it worked just fine.

I figured out that if you connect a energy extraction pipe to a energy cube it will pull the power out of the cube. Don't know about the power sources but it does work for the cubes.

OK, I'll see if I can work out why...

mekanism blocks wont connect to enderIO energy conduits either

Build 123 broke RF support, 122 worked just fine.

I'll test it again, my storage drive broke up and while waiting for replacement I can test in a clean instance.

Nope, I did a new instance on my other hdd. Downloaded all the mods that I had in my custom pack and tried the 125 build of Mekanism. Put down wind and solar generator, both started charging. Then I tried to put Redstone Energy Cell and a capacitor bank right in front of the generators, neither did accept power. Tried it with Ender IO energy conduits connecting them, no tranfer of energy. Tried Extra Utils energynodes, no transfer of power.
Mekanism universal cables won't connect to Energy Cells or Capacitor banks. Energy Cubes work with Mekanism cables, but if I replace the cable with energyconduit or energynode, it won't charge up.

I'm unable to replicate this in a dev environment.

You are correct. It seems to be some cross-mod interaction. Have been trying to isolate the cause, but don't have enough time today to test anymore and haven't found the mod that breaks the RF support.

I've found that solar and wind generators will connect to but not provide power to EnderIO's energy conduits and universal cables will not 'connect' to TE's energy cells but they will accept power from them and convert RF to IC2's EU.

Does the issue persist with a minimal set of mods installed? Everything is working fine for me with Mekanism 125 (master branch actually but they should be identical), BC 6.1.8, CoFHCore B8-36, EnderIO 272, FMP 314, IC2 653 Thermal Foundation B3-8 and TE B6-16. I suspect if it's not working for you it's probably a cross-mod interaction.

The odd thing here, is that ONLY mekanism suffers from not being able to transfer or use RF. Every other mod can do this fine.

Removing all of the cofh folders from .jar files that have it does work, however.

Found the offending mod: Asielib

Remove the 'cofh' folder from within asielib.jar and things should work.

well the issue also exists in the DNS Techpack, so if you can cross reference your mods with the mods in that pack, you'll likely end up with the offending mod

Try deleting cofh folders from other (non-cofh, obviously) mods. Someone's shipping the old version of their api.

A slightly more technical explanation of what the issue is:
CoFH's IEnergyHandler used to be the only relevant interface. It implemented IEnergyConnection but that was it.
IEnergyHandler -> IEnergyConnectionConnection
Recently the RF API was changed to split IEnergyHandler functionality into two different interfaces:
IEnergyHandler -> IEnergyProvider -> IEnergyConnection
_____________> IEnergyReceiver /
I've changed around our EnergyNetwork code to look specifically for IEnergyReceivers to put energy into. If another mod is shipping the old version of IEnergyHandler, it won't detect IEnergyHandlers as being instances of IEnergyReceiver so won't pass energy to them. Other mods not suffering from the issue have presumably just not updated their RF support yet.