I checked IRS refund tracker and shows that my refund delayed. What does this mean?

there are many possibilities. Only the IRS can tell you why.

Call 800-829-1040
1) Choose your language,
2) Then choose option 2
3) Then 1
4) Then 3
5) Then 2
6) When it asks you to enter your SSN or EIN do nothing – wait - - After it asks twice, you will get another menu
7) Then 2
😎 Then 3