yes, I am also facing same issue with LTE model. even though I put same sim during prebook and activation of tab, no chance it didn't worked. raised ticket in redeem support 180010 726 7864.i ordered on 9th June, received on 23 June 2020.
yes today it worked, ordered galaxy buds. one week after raised ticket it worked. till today morning I didn't get any email from samsung shop support about the ticket status. actually what I did I Uninstalled samsung shop app 3 days ago from tab, re installed today, i put same sim which i used for prebook in tab sim slot i tried to redeem offer, now samsung tab received OTP and auto read, got the offer. point is after first time sim insertion , wait for 3 full day then try.