I tried to search for Investec and I can see that it's already one of the Participating Financial Institutions. Although, I can only see the business banking account for this bank. If this is what you're looking for, make sure to:
Select the correct listing or try all possible links. Search by the banking sign-in URL to ensure you are using the correct listing.
Your bank does not connect to all types of accounts (for example, personal accounts vs business accounts).
If you're trying to add a different type of account, you can send a request to have it supported in QBO. Here's how:
Go back to the Banking menu and click Add account.
Type in the name of the bank and press Enter.
Scroll-down a little bit and select Request support for your bank.
Enter your bank's web address (URL) in the field provided, then select Request.