In `telnyx-node` 2.0.0-beta.5, `WebhookHeader` was declared as `string` although the implementation used `Uint8Array`, causing TypeScript errors when calling `verifySignature`. Check the installed version, then upgrade to 2.0.0-beta.6 or 2.0.0, where the issue was fixed. Avoid a cast as the first response to this version-specific mismatch.

This entry covers the reported beta.5 type mismatch; it does not diagnose unrelated errors in newer SDK versions.