If you signed the papers in 2019 and received the payout in 2019, that's when the new loan started. The money you borrowed its not taxable income, of course. You won't be able to deduct PMI, if you paid it, because PMI on a refinance must be spread out over 84 months and you didn't make any payments in 2019. You probably paid a few days of interest at closing, but that is only deductible if the HELOC includes acquisition debt. Interest on equity debt is not deductible.
Then, if your old loan was not recorded as being paid off until 2020, you will probably get a 1098 for that loan next year showing a small amount of interest paid. That will be deductible mortgage interest next year, assuming it is qualified acquisition debt.
