When exporting, remember to select the Detail table as the primary table (so, probably, PO_PurchaseOrderDetail in your case), on the Configuration Tab in Export Job Maintenance, and select the fields from the Header and Detail tables you want on the Data Tab. That being said, I don't generally try ODBC exports, too many moving parts. I export to CSV and then pull into Excel (assuming Access is similar).

What does your Access file look like when you try to link the table?  Do you get an error?

"I know I can get the data via linked tables, but it doesn't allow me to do what I need after the fact. "  - OK explain yourself here.  If you can link you can create a make table query based on the linked table so what is the issue. And you say it will not allow you to do what you need, what do you need to do? 

If you are trying to IMPORT the data from Sage 100 to MS Access (using the ODBC connection) which sounds like what you mean? or are you trying to Export a Report to MS Access via a Sage 100 "export to" option of some kind?...have you referred to Knowledgebase article "How to import data into Microsoft Access or Excel from Sage 100" (article # 51308)?  a short summary of steps for MS Access would be: 

Microsoft Access:

1. Select File, Get External Data, Link Tables (or 'Import').
   Note: If 'Link Tables' is selected, the data can be viewed but not changed. 'Import' will create a new table within Access that can be edited.
2. Select ODBC Databases() from the 'File of Types' drop-down box (Usually the last item listed).
3. The Select Datasources window should appear and default to Data Sources in the 'Look in' field.
   Note: If 'ODBC Databases()' is not listed, reinstall MS Access with ODBC Functionality selected.
4. Select SOTAMAS90.DSN and click OK
5. The SOTAMAS90 'User Login' dialog box should display, log on to the Sage 100 ERP database
6. Select the desired table and click OK. The table will appear in the Tables section of MS Access.

This only works in Sage 100 Standard/Advanced as Premium does not use that SOTAMAS90 ODBC connection.  If you link to detail table you should see data.  You may also want to try importing same data into Excel (also in the Knowledgebase article above) to see if it is only an issue with MS Access.  note: if 32-bit Access and 32-bit Sage 100 then it should work, if 32-bit Sage 100 and 64-bit Access you would need to install 64-bit ODBC driver for Sage 100, and if 64-bit Sage 100 then it should work with 64-bit Access - if not there could be an issue there that needs to be tested further.

Pushing data from Sage into MS Access is hard, and not recommended unless you are a skilled programmer.

Pulling data into MS Access from Sage (ODBC) is much easier for sure.

Sorry, I should have been more clear, in how I was doing it. I am using V/I to export the data via the ODBC. Unfortunately the linked table or import to access via access natively wasn't an option in my use case. I did through trial and error solve my issue. I started over and setup a new table with all fields as short text, limited the field names to 8 characters or less and limited the number of fields I was pulling from both PO header and detail, where originally I was pulling all fields from both in case they wound up being needed later.  My gut tells me it was a combination of the 3 things, but once I had what I needed it didn't feel like testing the number of fields, but in case someone reads this later, I figured I would include the information. Thanks to all who tried to help!.

VI exports are very awkward and the alternatives are plentiful, more flexible, and easier to work with.

Agreed, and I usually avoid them at all costs, but it gets the job done for this project which had very specific requirements. The good news was I got it working and the customer has what they need.