Same thing happened to me
I had the identical problem after performing the same mods. On the lower left side there is a plug (maybe 8 connector?) that goes to all the solonoids. Two wires had pulled out of the bottom of the connector, but not enough so that you could see them until you pulled the connector out and turned it over. A difficult diagnosis and a difficult fix. I hope this is not the same problem you have, but thought I'd mention it so you could check.
I had the identical problem after performing the same mods. On the lower left side there is a plug (maybe 8 connector?) that goes to all the solonoids. Two wires had pulled out of the bottom of the connector, but not enough so that you could see them until you pulled the connector out and turned it over. A difficult diagnosis and a difficult fix. I hope this is not the same problem you have, but thought I'd mention it so you could check.