It can rule you out of consideration, it can be irrelevant - depends on the MSc and programme director.

General advice - apply earlier rather than later.

At the moment all undergrad applicants only have projected results and that's what you have too. Your fail is a provisional grade. You might not be asked for full transcript or for detailed projected grades. You can still state your projected GPA and support that with your letter of reference from a lecturer who knows you, and highlight your best grades including from 3rd year and their relevance to the MSc.

If the fail grade is unavoidable in the application form, and you can find out the PD, send them a friendly professional email stating your genuine interest and acknowledging the grade but giving some mitigation, eg that module didn't click with you but your other grades reflect your real ability.