Can’t open JPEGs from photoshop 2019

Yes, you always need a file extension. 

Looks like the naming in the photoshop save dialog box is the issue. If I go back now and add .jpg to the end of the file name it will work on my phone.

How do you save the file from Photoshop? A MacOS screenshot is not a JPEG by default. I believe it's a PNG. And make sure you have updated Photoshop: https://feedback.photoshop.com/photoshop_family/topics/photoshop-file-extension-ex-jpg-not-changing-during-format-change

Alright, the plot is getting thicker. In finder the file type says it's a jpeg, even though photoshop didn't add a file extension to the file name. If I then attach it to an email on my mac to myself and then download it back onto my mac, then the file type says "TextEdit" but my mac will still open it. The files that I'm currently reffering to started out as screenshots on my mac, then I opened them in photoshop, edited them, then saved as a jpeg. If I airdrop them to my iphone X it does not give me the option to save to photos, only to files. Then it will not open the image and appears to be a text file or something. This is starting to look more like a mac issue. Running OS 10.15.1 Catalina. 

iPhone and iPads now take photos in HEIC format which is not supported by a number of applications including Photoshop. If this is your issue, the following article may be useful. It essentially advises the use of other aps that can convert the HEIC file to another format.

https://heic.imobie.com/how-to/open-heic-in-photoshop.htm

Make sure the image really is a jpeg. Apparently there is a bug in Photoshop on MacOS Catalina where Photoshop can use the .jpg extension but will still save in the previous format of that file if you click on a file name to use that name. See https://feedback.photoshop.com/photoshop_family/topics/file-name-and-extension-higlight-when-saving-on-osx