Saved JPEG is Dull and lacks contrast

Question

I have just got a new MAC because pS / lr wouldn't work properly on my old laptop. 
 
Have just done a black and white shot and it looks great in Lr but when I save it as a JPG, it's dull and flag and has lost all the highlights and shadows and tone. 
 
But when I view it on a phone, it looks like the edit on lr! 
 
So why is it showing so crap on my computer and not showing how it is on lightroom? 
 
It's one thing after another after another with lr and ps and am thoroughly fed up. 
 
Please can anyone explain what the issue is here. 
 
Have attached a screenshot shot showing how it looks in lr on the left as you're looking at the screen and how it appears when viewed on my computer on the right. 
 
Thanks

johnrellis · Answer

The screen photo shows you're using the cloud version of Lightroom, but you've posted in the Lightroom Classic forum. Either repost your question in the Lightroom (cloud) forum, where you're more likely to get a helpful response:

https://community.adobe.com/t5/lightroom-ecosystem-cloud-based/ct-p/ct-lightroom?page=1&sort=latest_replies&lang=all&tabid=all

or wait a while for a moderator to perhaps move it there.

Also, post a screenshot made on your Mac rather than with a phone, which will help others see the issue more clearly:

https://www.lightroomqueen.com/community/help/createscreenshot/

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