Trouble installing Catalina on Mac Pro 5,1

Running a mid 2010 Mac Pro 5,1. Just upgraded to MSI Radeon RX 580 to run Mojave. Now I’m following Dosdude1’s instructional on installing Catalina on an unsupported Mac. I’ve gotten through every step and am stuck on “installation requires downloading, try again later” or something to that effect. Any help would be appreciated, sorry if this has been asked and answered before.

submitted by /u/Over-Cash-3340
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