The IRS is claiming I didnt do my taxes in 2018 how do I open 2018 I pressed see all returns and it only goes back to 2019?

many have multiple accounts. 

see this link for a/c recovery

https://ttlc.intuit.com/turbotax-support/en-us/help-article/accountant-access/forgot-user-id-password/L4za3Ln1j_US_en_US 

It's common to end up with multiple accounts. First LOG OUT of whatever TurboTax account you're logged into right now. Then use this TurboTax account recovery website to get a list of user ID's for an email address. Run the tool against any email addresses you may have used
https://myturbotax.intuit.com/account-recovery/

If you used the Desktop CD/Download program then the only copy is on your computer and not saved or stored online.

Or is the IRS saying you didn't pay a tax due?

If you don't find your 2018 tax return in a different account, see the following FAQ for some other possibilities.

Why can't I find my return in Tax Home or My Docs?

Did you use TurboTax to file your 2018 tax return? If you used other software, or someone prepared the return for you, it won't be in TurboTax.

Of course, if you can't find your 2018 tax return anywhere, there is one last possibility. Maybe the IRS is right. Maybe you never filed for 2018.

or did you use the TT Desktop version for 2018?  If so, look on your computer hard drive.

And....does the IRS say you did not file for 2018---or that you did not pay your tax due for 2018?   If they are saying you did not pay the tax you owed, then your only proof that you paid will be your own bank or credit card statements showing the payment.