Why have i not got my refund?

Are you asking about 2018 online tax returns?   How did you file--did you efile, or did you choose to print, sign, and mail the returns?

Log into your online account.  At the Tax Home in the left column click on "Previous Taxes."  Choose tax year 2018.   What is shown for "status" of the Federal return (and state, if applicable)?

I see you have a duplicate thread on this same topic.   See the info also left for you there:

https://ttlc.intuit.com/community/after-you-file/discussion/when-will-i-recieve-my-tax-return/01/961652