I upgraded Photoshop to 2018 and can no longer open the software. I had to downgrade back to PSD 2017.1.1 in order to open files. This is also the case with the upgrade to Illustrator. I upgraded Premiere, AfterEffects, Media Encoder, all with no issues. Anyone else having this issue?
MAC OS 10.11.16
Are you getting any specific error message while opening the PSD files in Photoshop CC 2018 version? The PSD files you are looking to open, are they created in the older version of Photoshop?
Mac OS update shouldn't be the problem but if you are looking to update the mac os then, you can try using the Photoshop CC 2018 after the update.