dran sein
to be up
Colloquial for being one's turn to do something.
Ich habe die letzte Runde bezahlt, jetzt bist du dran.
I paid for the last round; now you're up.

on it / attached
Loading your saved state.
to be up
Colloquial for being one's turn to do something.
Ich habe die letzte Runde bezahlt, jetzt bist du dran.
I paid for the last round; now you're up.

'Dran' is the colloquial short form of the adverb 'daran' (on it / at it). It is used very frequently in spoken language instead of 'daran', especially in fixed expressions with 'sein' (to be).
Denk dran, die Blumen zu gießen!
Remember to water the flowers!
The word 'dran' clearly belongs to colloquial language. In formal or written texts, you should use the full form instead or a suitable paraphrase.
Wer ist als Nächstes dran mit dem Vortrag?
Who's up next with the presentation?
The most common meaning of 'dran sein' is that it is one's turn. This can refer to games, tasks, or a queue.
Du hast gewürfelt, jetzt bin ich dran.
You rolled the dice; now I'm up.
The phrase 'an etwas dran sein' means that you are currently working on something or pursuing a problem. The preposition 'an' followed by the dative makes this meaning clear.
Ich bin an einer Lösung für das IT-Problem dran.
I'm working on a solution to the IT problem.
there / with you
'dabei' and 'dran' can both have to do with an activity or situation, but they do not mean the same thing. 'dabei' says that someone is taking part or is currently in the process of doing something. 'dran' is colloquial and often means that it is someone's turn or that someone is currently working on a task. Learners may confuse the words because in both cases you are talking about a current action. The important point is: 'Ich bin dabei' often means 'I am taking part' or 'I am working on it'. 'Ich bin dran' often means 'now it is my turn'.

Bei der Besprechung ist sie heute als Erste dran.
In the meeting today, she is up first.
Beim Training war sie dabei, obwohl sie noch leichte Schmerzen hatte.
She was there at training, even though she still had slight pain.