Selected but no offer

After 2 weeks and 4 rounds of interviews, the HR informed me on Friday that I’ve cleared the last round and have been selected. S/he asked me to share some documents and told offer letter will be shared in 2 days. I waited for 2 days and called the HR today. Here’s the interesting thing, on calling s/he didn’t recognise me first and asked me which department I’m from, then asked to wait 15 minutes for callback as s/he was on break. Again waited for more than an hour and called back but this time s/he didn’t pick up the call. My question is should I be worried? Move on or am I being impatient? Just some more info - I don’t have any other offer in hand and the CTC I’ve asked for 100% of previous (last appraisal in 2021) although it’s still less than what is being offered for senior role in current market scenario in Bengaluru. Could this be the reason? Your thoughts, please.