"Re: I wasn't able to transfer a file from 2018 to 2019. I need to get the taxpayer's IPP number. Is there anything I can do?"

Whats an IPP number?  And how does transferring from 2018 to 2019 play into this?

IPP is identity protection pin and is good for one year only.  Your client should have received a new IPP letter in January of 2020 for tax year 2019.