I think I hit similar with my Contentment code... I ended up adding the

security

options:

await tryExecute(this, umbHttpClient.get({ security: [{ scheme: 'bearer', type: 'http' }], url }))

https://github.com/leekelleher/umbraco-contentment/blob/dev/v6.x/src/Umbraco.Community.Contentment.Client/src/property-editor-ui/data-list/data-list.repository.ts#L91