8dpo morning negative afternoon positive?

Alissa โ€ข Mommy of 3๐Ÿ‘ฉโ€๐Ÿ‘งโ€๐Ÿ‘ฆ ๐Ÿ’™๐Ÿ’œ๐Ÿ’™ two handsome kings and a beautiful queen ๐Ÿ’™๐Ÿ’œ๐Ÿ’™ 4 in heaven ๐Ÿ˜ฅ

Took a test with fmu, negative. Just did one now, and theres definitely no questions asked a faint line there. Why didnt it show up this morning?