Odessa and Cheryl,
Thanks much for the responses. Actually, I should label them resolutions, since I was able to resolve this challenge.
I had been doing as Cheryl suggests to be "on" the PI's research team, where I could write the amendment and attach documents. I still had to have the PI push the actual submission, however. Using Odessa's workaround (more on that later), I completed the task in less than 5 minutes.
At first, it didn't work, because I had not created an actual change. The system needs to see something different and register that as the amendment. During implementation, Odessa and I created a textbox to gather random notes and thoughts. This turned out to be perfect as the place to document what I would call an administrative amendment.

So, I wrote into the box the details of the admin amendment, which was much the same verbiage as the reason for the amendment. That was recognized as the change and I proceeded to approve.
The PI received the notification of an approved "admin" amendment, too. She was advised why the IACUC office made a change to her protocol. All very nicely documented.
Would it be handier to do this all within the amendment reason textbox, where the IACUC admin has a special button to approve? Yup, and I'll put that into the product suggestion area.
It's good to share this fix.
Finally, to Cheryl about our weather in SoCal. Already rather warm (reached the 90s yesterday). Fire season has started and we are once again in drought times.
Bruce