Offer Decline

I just had my first offer decline! I am so disappointed. It sucks because the sellers had 48 hours to accept the listing agent called literally right at 7pm the cut off time to verbally accept and said the paperwork would be sent this morning. Well my agent calls and says the listing agent called back and apologized for not reading the offer thoroughly but the sellers declined due to my closing cost request of $5000.

So it's like double the disappointment. I'm not sure why he wouldn't read it completely but I decided not to counter because this agent feels a little shady. Yesterday he called and asked if I would like to up my offer to the highest and best but with no additional details. I said no and it was verbally accepted at the last minute.

Now im wondering if I should've offered no closing costs.

Opinions??