For me, it was my second internship. The main thing I remember is the stress of not being able to do any work while I waited for access to some of our systems. Feeling imposter syndrome as an intern is a given, but it's only made worse when you can't even start doing your job, let alone deliver anything of significance.
Was supposed to start on Monday. Was told that Monday morning, I would get my passwords and everything to log in and get set up. At 10AM, I emailed my contact there as I knew nobody else (one of those companies where interviewing isn't always done by the same team). He didn't get back to me until Tuesday. Spent the day wondering if I had been ghosted and pondering whether to tell the other companies I turned down that the job fell through.