I usually put images into an album. Once you select the upload to album option you can then drag or copy and paste as many images as you want from your file directory to the upload "box" and then hit the upload button. I just dumped 25 as a batch a few minutes ago.
Just to close the loop on this....
Today, I went back and tried to upload multiple images to the library from my PC, selecting several individual images and the Image Gateway batch loaded each image simultaneously without a hitch.
It's weird that it wouldn't do this before.
07/31/2023: New firmware updates are available.
05/31/2023: New firmware updates are available.
05/18/2023: New firmware updates are available.
04/20/2023: New firmware version 1.4.1 is available for EOS R3
03/30/2023: New firmware updates are available.
2/07/2023: New product announcements!EOS R8 EOS R50RF-S55-210mm F5-7.1 IS STMRF24-50mm F4.5-6.3 IS STMRF15-30mm F4.5-6.3 IS STM