After a few trials of deleting and adding manually downloaded packages, I was able to work around this error. Within Studio’s package manager, I installed each package one by one and determined that the UiPath.Excel.Activities package was causing the “Nuspec file does not exist in package” error even though I confirmed it existed.
Although this allowed me to continue work on my project and issues were no longer found with the dependencies, I’d prefer that this be solved properly rather than a workaround to avoid future meetings with this error or something similar. I’m reaching out to my IT team to discuss potential firewall/proxy interference and will continue to search for a solution. For others that may run into this issue and are unable to solve with a workaround, I will try to keep this post updated with any findings!
Thank you to all who replied and offered suggestions!