Azure Devops Storage - dataService undefined

I'm following on from the various examples on the microsoft website for devepos extensions, but the one for creating and editing documents does not seem to work for me (https://learn.microsoft.com/en-us/azure/devops/extend/develop/data-storage?view=azure-devops)

window.requirejs.config({
    enforceDefine: true,
    paths: {
        'SDK': './lib/SDK.min',
    }
});

window.requirejs(['SDK'], function (SDK) {
    if (typeof SDK !== 'undefined') {
        console.log("SDK is defined. Trying to initialize...");
        SDK.init();
        SDK.ready().then(() => {
            console.log("SDK is ready");
            // Get data service
            SDK.getService(SDK.getContributionId()).then(function (dataService) {
                // Prepare document first
                var newDoc = {
                    fullScreen: false,
                    screenWidth: 500
                };

                dataService.createDocument("MyCollection", newDoc).then(function (doc) {
                    // Even if no ID was passed to createDocument, one gets generated
                    console.log("Doc id: " + doc.id);
                });
            });

        });
    } else {
        console.log('SDK is not defined');
    }
});

After calling SDK.getService, dataService is always undefined. As far as I can tell, the SDK has initialised correctly because many of the other SDK functions seem to work as expected, and the contributionID is correct. But I don't want to rule that out as a cause since I had a lot of trouble getting rid of the 'No handler found on any channel for message:' error.

Any help or suggestions is much appreciated.

I noticed some others had the similar issue with dataService. There is a repo which seems to be working. Hope it's helpful for you.

    private async initializeState(): Promise<void> {
        await SDK.ready();
        const accessToken = await SDK.getAccessToken();
        const extDataService = await SDK.getService<IExtensionDataService>(CommonServiceIds.ExtensionDataService);
        this._dataManager = await extDataService.getExtensionDataManager(SDK.getExtensionContext().id, accessToken);

        this._dataManager.getValue<string>("test-id").then((data) => {
            this.setState({
                dataText: data,
                persistedText: data,
                ready: true
            });
        }, () => {
            this.setState({
                dataText: "",
                ready: true
            });
        });
    }