Why am I unable to import data from external sources, and how can I troubleshoot this problem?

We use to Import data from other sources only through the Excel ,please follow below steps: 
Steps for Import Master from Excel:
Step 1:   go to the Administration tab and click on the Data Export Import.
Step 2: Choose the Import Master from MS Excel option and select the type of master that you want to import, such as Items, Accounts, etc. 
Step 3: Here, you need to map the fields in BUSY with the columns in Excel. 
Step 4: After mapping all the columns, select the Excel File Path and enter the Starting & Ending Row and Sheet Number of your Excel file. Then, click on the Import button and wait for the import process to complete.
Steps for Import Vouchers From Excel:
Step 1:   go to the Administration tab and click on the Data Export Import.
Step 2: Choose the Import Vouchers from Excel option and select the type of voucher that you want to import, such as Sale, Purchase, etc. 
Step 3: After selecting the voucher type, click on the configure button and create a format for the voucher. Then, map the fields in BUSY with the columns in Excel. You can select the fields from the drop-down list and match them with the Excel columns. 
Step 4: After mapping all the columns, select the Excel File Path and enter the Starting & Ending Row and Sheet Number of your Excel file. Then, click on the Import button and wait for the import process to complete.