Prusa Slicer 2.8.0 to Prusa XL Firmware 6.0.3 - Get Error 28 and Cannot Transmit File  

Prusa Slicer 2.8.0 to Prusa XL Firmware 6.0.3 - Get Error 28 and Cannot Transmit File

After upgrading to the new version of PrusaSlicer (2.8.0) on Mac (latest OS version). Using firmware version 6.03. on a Prusa XL 5 head printer, I have been encountering a persistent error when trying to upload the Gcode to the printer using the upload button on the Plater screen in PrusaSlicer. The error is "Upload has failed. There is no suitable storage found at xx.xxx.x.xx (its IP address). blah blah [Error 28]. 

A USB memory stick is installed when this occurs, and I can upload to it using the Prusa Connect feature that has been incorporated into PrusaSlicer. I can then print the file through PrusaSlicer Connect functions (usually, get a variety of issues with this function at times too). Based on being able to upload to the machine using PrusaSlicer, I can establish that 1) Printer has network connectivity, 2) I can upload files to it even though cannot upload from the Plater screen, 3) there is a USB memory stick installed and functioning. I can find the upload files, select them and print if I wanted to do that (I want to upload and have it start printing).

So absent a network issue and printer connection issue (I am connected, can see the printer information in PrusaSlicer Connect functions, what is going on? Never had this issue before the most recent software updates. No changes to my network have occurred and I can easily establish a session to monitor the printer status, etc. Somewhat new to Prusa world, so be gentle please.