Do you mean you can't login to desktop and mobile with the same details at the same time?

you can, but it logs you out of 1.

So for example, I'm logged in on my desktop browser using chrome.  Then I go to login on my mobile device - I stay logged in on both but close my browser on my desktop since I'm now logged in on my phone, but when I return to my desktop and go to my website again (even though I should be logged in) I'm logged out...Same applies the other way around.

How long are you absent from desktop or mobile browser? If it is 30 minutes then you're automatically logged out, this is how sessions work

I understand that, but if that's the case, it should log me out of my desktop view after 30 minutes of having the browser closed without being logged into anything else but it doesn't...

Very odd.

Is there a way to change this somewhere in the code to allow users to stay logged in on different devices (at the same time)?

Well, that means your cron jobs are not properly configured. 

as to the staying logged in please check here: http://www.oxwall.org/forum/topic/12138?page=1#post-61264

I have the same issue. Once I log in from another device the previous session is lost. Example: I'm on my laptop and logged in. I decide to move to my tablet and log in from there once I go back to the laptop I have to log in again. This is very annoying. Why can't be logged in from different devices? It's not the cron. It's oxwall.

Emil what version do you use on your tablet? mobile or desktop?

1.7.4 thanks.
It is a weird issue. Maybe it is cookie based?

It even appears if I use an Apple Webclip on iPhone. If I log in from the webclip app and then click a link it opens Safari and the session is lost. I have to log in again in Safari.

To me this problem is related to https://developers.oxwall.com/forum/topic/38467.

I proposed the following idea to gather votes:
https://oxwall.uservoice.com/...ltiple-devices-login