Hi,

"Theoretically, Cronbach’s alpha results should give you a number from 0 to 1, but you can get negative numbers as well. A negative number indicates that something is wrong with your data—perhaps you forgot to reverse score some items. The general rule of thumb is that a Cronbach’s alpha of .70 and above is good, .80 and above is better, and .90 and above is best."

Reference: https://www.statisticssolutions.com/cronbachs-alpha/

Bhogaraju Anand thank you for your answer, but I still don't know what to do. should I keep it or reject it?

Ps. There is no problem with coding the scores or something like that.

Recheck right from the scale, scoring pattern and each individual case one again.