SHENZHEN, China/HONG KONG—Chinese property developer Kaisa Group Holdings Ltd. said on Thursday its finance unit had missed a payment on a wealth management product (WMP), adding to worries about a cash crunch at the debt-strapped company. Kaisa’s troubles come amid concerns about a deepening liquidity crisis in the Chinese property sector, with a string of offshore debt defaults, credit rating downgrades, and sell offs in the developers’ shares and bonds in recent weeks. The Shenzhen-based developer, which provides a guarantee for the wealth management product, said in a statement it is facing unprecedented liquidity pressure due to a challenging property market and rating downgrades. It said it was raising funds to ease the pressure by measures including speeding up asset sales. It is ranked as the 25th largest developer in the country by home sales. Kaisa has the most offshore debt coming due over the next year of any Chinese …