Muhmad if temperature, humidity and light were ok, the most likely cause is a contamination by an other fungi like Trichoderma or a bacteria.

I think the environments should be not optimal for the developing the fruiting body. Other fungi and bacteria could be attack the straw mushroom’s pins. Please read this article: ‘Cendawan Kontaminan Dominan pada Bedengan Jamur Merang dan Interaksinya dengan Jamur Merang Secara in vitro’ Jurnal Mikrobiologi Indonesia 4(1):14-18.

thank you Roberto and Bu Gin