can't change account from expense acct #5700 to prepaid expense acct #1300 in AP purchase invoice

Hi,

I entered an AP purchase bill for Dec. 31, 2020 in Jan. 2021. I had recorded it in expense acct #5700 originally.

Later we knew it should be prepaid expense .

So I created prepaid expense acct #1300. But I can't change the AP purchase from #5700 to #1300.

I saw #1300 in the Chart of GL. But when I edit the AP purchase, I can't find the #1300. 

#1300 is set like this today:

Thanks a lot!