One-time passcodes delayed from corporate

For the past three days, OTP codes from multiple sites have failed to arrive in a reasonable time. In some cases, long-delayed messages from various senders arrive at once. For example, tonight's codes from Amazon, Xfinity, Whole Foods, and others arrived at exactly 10:07 p.m. Some were requested hours ago; for Xfinity, they were requested almost 24 hours ago. This issue affects only OTP messages from corporate entities; messages from private individuals are unaffected.

I have no idea where the bottleneck would be.