Once initial disclosures have gone out on a loan, the Loan Calculator and its letter generation are locked. This is one instance of a general rule: a disclosed loan is frozen for editing across the POS. See article 64, what locks on a loan after disclosures are issued, for the full list of what freezes and why. This article covers the calculator-specific part.
What is locked
The Loan Calculator itself, along with generation of Prequalification and Preapproval letters from it. A notice on screen explains why.
What still works
The Loan Comparison tab stays readable, so you can still walk a borrower through a comparison you produced earlier.
On the mobile app
The same lock applies in the app. Worth knowing separately: in the app, pre-approval letter generation sits behind the three-dot menu at the top right of the Loan Calculator rather than on a visible tab. That is a common reason the option is reported as missing on a loan that is not in fact locked.
If you still need a letter
Produce it from Encompass on a disclosed loan. If the letter names only one borrower when you expected all of them, check which template you selected first — lenders commonly maintain several pre-approval letter templates and they do not all address every borrower on the file.
What support will ask for
Whether initial disclosures have been sent on the file, and which template was used if the letter's content looks wrong.