However, if you're accessing QuickBooks through the browser, you can try opening it using a private window and create projects from there. This can help us verify if the issue is browser-related.
Web-based platforms like QBO gathers data which often leads to bog down processes and performance issues. If your now able to generate projects, go back to your regular browser and clear its cache. This will let you utilize QBO in a clean slate.
You might consider using these guide on how to use projects and invoicing customers for project expenses: