Please post a screen shot of the external editing settings, dialog window.
If you have PS installed you shouldn't need to use the secondary external editor setting to send an image from LR to PS.
In the past, which has worked for me, I edit my business photos in the "Edit in Adobe Photoshop CC 2017" Editor in the top of the Preferences / External Editing window with settings of Tiff/ProPhoto RGB/16bit 240 Resolution. These match the way PS is set up.
My family photos I use the Additional External Editor set to Photoshop, using settings: Tiff/AdobeRGB(1998)/8 bit/300 Resolution.
This has always worked for me in the past, changing the settings automatically in PS to match. Now it always opens with the window saying that the Embedded: Adobe RGB (1998) does not match the current RGB working space ProPhoto RGB.
So when you right click do you have 2 entries for PS listed?
Also I just tried to assign PS 2017 in the Additional External Editor section and I get this warning box.
I click the Use Anyway button and it goes through. Then when I right click I get this.
When I select that PS opens and the images is loaded with the setting I set in LR.
Maybe make a new Preset and test.
I am wrong. It is supposed to ask me if I want to edit in the different color space etc. I just say yes. Sorry for the inconvenience.
Thank you for your help!!