Would-be Craigslist competitor OfferUp has been trying to raise about $100 million in financing for at least five months, according to people with direct knowledge of the situation. It’s been tough going, a sign of how quickly tech startups can lose popularity among investors.

Prominent tech investors, including Sequoia Capital and SoftBank, have passed on the round because they think the valuation being sought is too high—particularly given increasing competition in the mobile marketplace sector, said the people. The exact valuation OfferUp is seeking couldn’t be learned. OfferUp is currently working with Morgan Stanley to find new investors, said two of the people, who declined to be identified because the information is confidential.