
Mark T. answered 03/21/19
Career nuclear engineer, professional instructor, Lightroom expert
I do the LR/PS round trip TONS!
I get that error occasionally. I've never figured out why bc for me one trick always fixes it. I close PS and reopen it. That doesn't seem to be working for you. It'd be difficult to troubleshoot by just me wirint text once but any troubleshooting requires isolating possible issues. So the first step would be to I'd try a basic round trip and see if there is a problem.
Open LR, select a image, click Edit in PS, make a basic change like drawing on the image with a brush. Then click File Save. This SHOULD create a .psd (depending on setting) and add it to your catalog in LR.
If that doesn't work then I'd check you LR External Export presets for a colorspace that matches the working colorspace of PS. That's the most obvious issue cause by upgrading. There are other compatibility issues but it's on PS's preferences side. Read the PS warning on LR's external export preferences window. Follow that inside PS.
Again, this is a finicky issue I deal with often with PS, especially when I've been doing a lot of crazy things with PS. But for me it's fixed by closing and opening PS.