Ps4 Pro HDR help needed

If someone could help me out here. I would really appreciate it. I've bought a new tv. Samsung 55MU7000 (MU8000 in the US I believe). I've also bought a ps4 pro to use on my new TV. No matter what I try, I cannot get the Ps4 Pro to output HDR on the TV. I've read the whole internet to try and figure out how to fix this and I've read a few posts from people who have had the same problem on other Tv's. But they stop short before a solution is posted. I've got all my pro picture settings on Auto. It's showing that it's set to 4k resolution but that my TV doesn't support HDR. I know it does. HDR10 I believe, it's why I bought it. I know that on my TV there is a HDR+ picture mode in expert settings which has nothing to do with actual HDR. It's just a mode that can be enabled. I know that under General settings on my TV there is a menu called external device manager, and that in there you have to turn an option on called UHD Color for each HDMI port you have connected and want to use with HDR. It's here that I have the problem. With this option turned off my ps4 pro works great. It even says that it's in 4k resolution. But as soon as I turn the UHD Color on, to enable HDR, the source cuts out and I get a black screen, then the no source detected screen. I have to turn the UHD Color off for that HDMI port and then the source starts recognising again. I've tried every HDMI port. I've tried 4 different HDMI cables, including the one that came with the Pro and two brand new ones. The last one being premium certified and stating it's compatible with 4K HDR on the box with an 18gbps speed. None have worked. (This was the only solution I did find where someone said it worked after buying an expensive cable) I have tried power cycling. Changing the UHD Color setting for the port BEFORE plugging in and turning on the pro. Unplugging everything and waiting then setting it up again. I've factory reset my TV. Both my TV and Pro have the most up to date firmware. I've booted the pro in safe mode and changed the HDCP to 1.4 and tried all of the above. I've rang Sony and Samsung. Samsung I've rang 5 times now and probably spent 3 hours trying different trouble shooting with them controlling my TV. They told me to buy a gold plated cable. Didn't work. I'm waiting for one of there 'product specialists' to ring me back. The only thing I can think to ask is can you not turn these settings on until you have a game with 4K options running on the pro? I mean I've loaded up resident evil 7 which has a HDR brightness setting which is greyed out. So it can't be that surely? Can anyone offer me a solution to this? I've spent close to 1600 English pounds on all this, so I can play in 4k and HDR. And it's giving me a sick feeling that I can't get it to work. Any advice appreciated. Thanks