What version are you running?  Modern versions have a new utility to help with the Paid Today flag, but older versions require a messier process (noted in the Sage KB).

2019 premium 

See the Additional Information section of KB 18024

https://support.na.sage.com/selfservice/viewdocument.do?noCount=true&externalId=18024 

I think I will open an case with Sage because this is a little more than I want to get into. I would be afraid of making a mistake. 

Thank you much for the KB

Well I tried on my own and when attempting B. option

1. Select Library Master, Utilities, Data File Display and Maintenance (DFDM)
2. Browse to "...\MAS90\MAS_XXX\APXXX\AP_OpenInvoice.m4t"
3. Click the Key Scan button to locate and select the affected invoice record.
   The key consists of the following:
   • Invoice number
   • Vendor number
   • Division number (00 if no divisions are used)
4. Click Edit, and select the Paid Today field
5. In the Change/Value field, change the Y to N and click OK/Update
   Note: Y indicates that the invoice has been selected for payment.

I got the following error 

Well I tried on my own and when attempting B. option

1. Select Library Master, Utilities, Data File Display and Maintenance (DFDM)
2. Browse to "...\MAS90\MAS_XXX\APXXX\AP_OpenInvoice.m4t"
3. Click the Key Scan button to locate and select the affected invoice record.
   The key consists of the following:
   • Invoice number
   • Vendor number
   • Division number (00 if no divisions are used)
4. Click Edit, and select the Paid Today field
5. In the Change/Value field, change the Y to N and click OK/Update
   Note: Y indicates that the invoice has been selected for payment.

I got the following error 

It looks like you're on Premium / SQL.  The KB article's point 2 is not right for you... instead of browsing to the M4T, just type AP_OpenInvoice in the File Name field and it should open the SQL table.

Sage,

Someone should update the KB to reference proper instructions for Premium (including a version reference to when DFDM was improved to allow SQL data edits).

No it doesn't after typing.. Can't I just use SQL to change PaidToday.. 

If you are comfortable doing that, and have access, yes... but if you are on Premium, and the M4T has current data, something is seriously wrong with your data dictionary.  That table should be in SQL.  Open a case with Sage to get them to fix it.

I went back into the instructed way in KB and for whatever reason I'm able to access the entry.

Nice!!! that worked... As always thanks a ton.. 

Ok I will do that thanks