Get POST 500 error when I try to enter "leaderboard.getRank(999);"

Browser: Chrome 115.0.5790.110
Operating system: Windows 10 Home 22H2
Node.js version: 18.17.0
Firebase Tools version: 12.4.6

Hi.

I'm trying to set up a leaderboard for a browser-based game I'm working on, by following this codelab. Everything seems to be working well until (and including) I enter into console
"leaderboard.addScore(999, 11);"

which logs:

"Promise {: undefined}
leaderboard.js:48 {data: 'Score created: [object Object]'}"

Then, when I try to fech the score by entering "leaderboard.getRank(999);" in console, I get the following errors:

"service.ts:224 POST https://us-central1-punk-rock-samurai.cloudfunctions.net/getRank 500
T @ service.ts:224
b @ service.ts:298
await in b (async)
(anonymous) @ service.ts:213
(anonymous) @ service.ts:219
getRank @ leaderboard.js:59
(anonymous) @ VM41:1"

and

"localhost/:1 Uncaught (in promise) FirebaseError: internal
Promise.then (async)
getRank @ leaderboard.js:60
(anonymous) @ VM41:1"

I would greatly appreciate any help or guidance on how to complete this codelab and get my leaderboard working.

Mvh. Erlend Kulander Kvitrud