For the past week or two, TB only downloads 3 or 4 (never more than 4) messages at a time from my Gmail. Now, instead of just starting TB and it downloading all new messages, I have to click Get Messages multiple times to retrieve everything. I have seen similar questions here and the answers have all been variations of blaming the user. So: a) I have not changed any settings. b) It used to download all available messages, whether when TB started up or when I clicked Get Messages. c) Just now on starting TB, it took 6 clicks to retrieve 20 message. They are all text, no attachments, so the total size would be in KB, not MB. d) Using Speedtest, my connection speed is over 300 MB/second so it isn't a connection speed limit on my side. And I doubt it is a speed limitation on Gmail's side.

With all of that in mind, I would appreciate any suggestions of what could be causing the problem and what the fix might be.