Hi there, @sweetsoutherngra and @z212123132. Let me share some information about adding bank transactions into QuickBooks (QBO) Online.
I agree with @4Gal, too many cached files can cause the browser to behave insignificantly. So I suggest performing our fellow community member's recommendation.
Additionally, if you have thousands of transactions processed previously, it could be best to upload them manually by month or quarterly in QBO for greater success rates. You can also convert it into a CSV file either 3-column or 4-column format if you can't still import the OFX file. In this manner, you can easily handle it since you can edit it using an Excel application.
Please make sure the data is in the correct format. This is to check that adding too many transactions must be one of the reasons or the file format you've created.
Furthermore, please check out this article for you to learn how to Import and export your CSV files in QBO: Import/export CSV files.
Let me know if you need anything else about your bank transactions in QuickBooks Online. Don't hesitate to comment below. Take care.
