Thanks for reaching out in the Community for assistance, @damian-damiancla. I’ll help you sort this out so you can successfully upload your CSV file to QuickBooks.
A stored cache helps your QuickBooks Self-Employed (QBSE) account to run quickly. However, it can cause the program or features to act weirdly or become unresponsive once corrupted. I’d recommend removing that historical data, so you can access QBSE with a clean slate. This action also helps us to verify if it's a browser-related issue.
To save you time, use either of these keyboard shortcuts:
Google Chrome: Ctrl + Shift + N
Safari 11 or newer: ⌘ + Shift + N
Mozilla Firefox: Ctrl + Shift + P
Microsoft Edge: Ctrl + Shift + P
If it works fine, go back to your original browser and clear its cache to start fresh. Also, please make sure that you're using a supported and up-to-date browser and have added Intuit as a trusted site to prevent your browser from potentially blocking site content.