As Dawn said, the 8x split amp they put in might not be MoCA compatible. The one she linked to should work fine.

Most TWC techs from what I hear are idiots and have no clue. At least with Comcast, I can kick out the stupid ones and I'll eventual get a good knowledgeable tech within 2-3 tries.
What you need to know here, is what all the readings are coming in = signal level, noise floor, MER & BER. If you don't have a good enough signal coming in, amplifying a bad signal is not going to fix anything.
You need a good meter to do this and if you haven't spent $2K+ for one then you are going to have to rely on the cable tech. You have to look over his shoulder, as sometimes these guys don't even know how to turn the meter on or even have one with them. In such a case, kick them out... next tech please.

It could also be the cabling in the house. Who pre-wired it? I had a house awhile back that had 12 drops in it (only needed to use 8), that was about 20 years old. I used one of those amps linked to above but I was still having issues with the cable boxes in the house.
Signal levels & quality coming into the house looked good. I was losing a lot of signal thru the wiring in the house (more than I should) but levels and quality were still marginal and should have worked.
Finally got a Comcast business tech out to the house after 4-5 other visits. He had one of their new Comcast branded meters (which has very nice) and we spent almost 3 hours going thru the wiring in the house. Turns out 4 runs in the house were picking up massive noise and bleeding it into the system. Ran new cable to these locations and all was well.
Big invoice to the customer but after many years of trying to get their cable TV to work right, they were happy to pay it.