Invoice Tracker will not load any invoices - Test Database

I have an issue in our test/development system of Epicor 10.2.6
I’m working on modifying an SSRS report, and need to print a copy of an invoice out of invoice tracker. However, whenever I try to load an invoice, I get the error “Could not load file or assembly 'Fsisp.Internal.SI.FSIARInvoiceGeneration … The system cannot find the file specified” . When I do a search and choose any invoice from the search results, I get the same error message. I know the invoices are there, they just refuse to load.
I’ve tried stopping and restarting the application pool, regenerating the data model, and recycling the IIS application pool. I’m really at a loss as to what to try next.
Has anyone seen this issue, or possibly know what to do to fix this? Thanks!