Loan is for a sfr rental property. Copy of appraisal was provided last Thursday and borrower acknowledged receipt. The appraisal notice was never given however. While it looks like there is a violation of not providing the notice in a timely manner, can the loan close today (Monday) or would the 3 business days be tomorrow?

You must provide the notice within 3 business days after receipt of an application, failing to do so is a violation. Providing it now does not negate that violation.

If the appraisal has been provided within the required time then IMO you can close.

There are lots of violations that simply cannot be cured. You can only learn from them and try to make your procedures as fool-proof as possible, and focus on getting the miscreants retrained on the requirements.

I'm a big fan of maintaining a record of who screws up which compliance requirements, and using it for remedial training and as a factor in performance reviews.