There is actually a Knowledge Base article about this error message. If you had gone to the Sage Knowledge Base this is what you would have found.

Verify that there are no Cash Receipt Deposits to update by previewing the Cash Receipts Journal.

1. Accounts Receivable, Main, Cash Receipts Journal, Print/Preview.
2. If using Batch Entry, verify that there aren't any open batches.

If there are no Cash Receipts to be updated, reinitialize the Cash Receipts data entry files by following this article, DocLink: How to reinitialize Accounts Receivable Cash Receipts Entry files:

1. Open Library Master, Utilities, Reinitialize Data Files.
2. In the Company Code field, select the affected company.
3. In the Module list, select Accounts Receivable.
4. Select the following files::
   • AR_CashReceiptsDeposit
   • AR_CashReceiptsDetail
   • AR_CashReceiptsHeader
   • AR_CashReceiptsRestart
5. Click, Proceed
6. Open Library Master, Utilities, Rebuild Sort Files.
7. In the Company Code field, select the affected company.
8. In the Module list, select Accounts Receivable, and then click Proceed.
   Note: It is not necessary to recalculate aging or open order amounts.

Note: If batch entry is used, delete the batch records from the GL_CompanyActiveBatch file.

1. Library Master, Utilities, Data File Display and Maintenance (DFDM).
2. Click the Browse button, and select ..\Mas90\MAS_xxx\Glxxx\GL_CompanyActiveBatch (xxx = company code).
3. Click the Key Scan button, and select A/R Cash Receipts batch records that share the following format:
   • Module code: 3 characters (Always "A/R")
   • Batch Type: 2 digits (Always "02")
   • Batch Number: 5 digits (#####, where ##### is a batch number)
     For example, the key "A/R0212345" would be a sample A/R Cash Receipts batch record for Batch Number 12345.
4. Click the Delete button.
5. Perform the steps above for any other valid A/R Cash Receipts batch record in the file.

Once the above steps are completed, attempt to process Period End Processing again.