429 Error Help

These article here says what that error means.  It sounds like it is actually Cloudflare protecting the system.

General scalability

Quickbase utilizes edge-layer protection with Cloudflare to ensure security and stability of the platform. Quickbase may return an HTTP error 429 in the case where an integrator is making too many requests in a period. Per the RFC spec, integrators should respect the 429 response code and the response header "Retry-After" that indicates how long the originator should wait before trying again.

As an aside, you should rewrite your call like this

"&_fid_40=now" &

The subtle difference is that the Now() will reflect the date/time that the page loaded (which may get stale), and the now will be the date/time that the API call is processed.

As an aside,   man-o man, they sure make a run for the exits at quittin' time eh?  Such a rush that Cloudflare is seeing it as an attack  :)