I apologize for the very cynical response. It can be frustrating.
Although I still completely believe this problem is easier solved at the source, which is to stop trying to spend time figuring out other people's browsers and simple provide links to part 1 and part 2 files right in the account. This would... in every case... make 100% certain...which is the kind of certainty you should aim for.... that no one ever has to ask this question ever again.
Since this wont be done.... there will be more questions like this again.
I appreciate the response... but there is also another solution which is to use the Autodesk "Desktop App" which will show you the needed updates available and download them and install them for you.
Though this is also not a great solution as it feels invasive on a user's computer as the edifice for having Autodesk software feels like a complete subjugation of one's ram, boot ini, etc just so that Autodesk can eat up even more real estate instead of trying to stay lean and easy on the users.
But... for the sake of future posters stumbling into this thread trying to find ways to download any "part2, part3" files etc... don't fiddle with your browser. It is a pointless affair. You will not find the "pop up blocker" that is referenced. This is not a solution under any circumstance and will lead you to waste too much time trying to find a "solution" that doesn't exist.
Just use the Desktop App, vs going to your Autodesk acct login (Which makes more sense actually), and the Desktop App will be your mommy and try to fix it for you.
If the Desktop App wont update it for you or the account login doesn't work I suppose you could go back to trying to find the "browser blocker". Good Luck... it doesn't exist.
On a positive note.... the update to 2020 that I downloaded DID fix the crashing with using Mash dynamics.
So thank you Autodesk and Co. for that fix.