Keyboard won’t print some letters

Which letters exactly?? That's really vital info to provide if you want help. If 789uiojkl, you just need to turn off Mouse Keys in accessibility preferences.

Which letters? Which exact Mac?

Is Mouse keys enabled?

https://support.apple.com/guide/mac-help/if-your-mac-doesnt-respond-to-key-presses-mchlp1240/mac

Does yours qualify for Keyboard Service Program for MacBook, MacBook Air, and MacBook Pro...

https://support.apple.com/keyboard-service-program-for-mac-notebooks

Eligible Models

To identify your computer's model and to see if it is eligible for this program, choose Apple () menu > About This Mac. Eligible models are listed below.

• MacBook (Retina, 12-­inch, Early 2015)
• MacBook (Retina, 12­-inch, Early 2016)
• MacBook (Retina, 12-­inch, 2017)
• MacBook Air (Retina, 13-inch, 2018)
• MacBook Pro (13­-inch, 2016, Two Thunderbolt 3 Ports)
• MacBook Pro (13-­inch, 2017, Two Thunderbolt 3 Ports)
• MacBook Pro (13-­inch, 2016, Four Thunderbolt 3 Ports)
• MacBook Pro (13-­inch, 2017, Four Thunderbolt 3 Ports)
• MacBook Pro (15-­inch, 2016)
• MacBook Pro (15-­inch, 2017)
• MacBook Pro (13-inch, 2018, Four Thunderbolt 3 Ports)
• MacBook Pro (15-­inch, 2018)
• MacBook Pro (13-inch, 2019, Four Thunderbolt 3 Ports)
• MacBook Pro (15-­inch, 2019)

Note: No other Mac notebook models are part of this program.

https://www.apple.com/support/keyboard-service-program-for-mac-notebooks/