Based on your comments I suspect you tried to import directly into the history tables.  Did you import into Invoice Data Entry and then post or did you import into the AP Invoice History and Detail History files.  Also have you checked to make sure you posted the Daily Transaction Register?  Go to General Ledger, Main, Daily Transaction Register and try to post and see what happens.

We import using an AP import job in the visual integrator, then we go to invoice register to post. We have done this every period closing.The invoices can be pulled up in Vendor Maintenance. When I Alt-Z into an invoice, I can see that the entry is posted in a Source Journal under the Main tab. When I Zoom into the Source Journal, it shows what ledger accounts the invoices are posted to. However, when I check the ledger accounts in Account Maintenance in General Journal, they don’t appear to be posted there.

I also tried checking the Daily Transaction Register, it's not there. My colleague tried to post it a week ago, we have struggling with this ever since.

This will sound silly, but are you sure you're looking in the right year in Account Maintenance?

Check the Accounts Payable Setup Options.  Be sure that the Integrate with General Ledger is checked.

This sounds kinda like you posted in the wrong year. Pull up the journal again and look at the year

If you post an AP invoice against the AP control account, there will be no GL entries.  Never do that.

Make sure AP is integrated with the GL (AP options).

Recognize that the AP invoice date is set independently of the GL posting date, and may be different.

Compare an invoice entered manually, to something imported using VI, both before posting.  That may help identify changes you might need to make to the VI job.

Seen this a number of times where the control account is used incorrectly.  Mostly when inventory is purchased with a credit card and they use the inventory account instead of COGS.

When importing, Visual Integrator uses an Account Key, which is like a 9 character encrypted value to display a fully formatted GL Account. Verify your sourcefile contains the fully formatted GL Account Number which includes the separators (123-45-6789). If the total number of characters, with separators  is over 9 characters, select "Skip Source Data Truncation" on the Configuration Tab otherwise only 9 characters of 123-45-6789 will be read and the import will just pad remainder with trailing zeros and will import to account 123-45-6700 instead.

You can run GL Detail by Source Report using the Register Number that was generated on the AP Invoice Register after the import to see which GL Accounts were actually posted in GL.

I suspect the GL Daily Transaction Register was empty because of a recent new security role "Allow Automatic Update of Daily Transaction Register"