I'm afraid there is not enough information to give you any definitive answer.

"I can't pay" could mean about 4 things off the top of my head. (don't have enough money in the account, can't find the vendor, can't see the invoice when I select the vendor, it won't print a cheque, once completed the cheque won't post)

Is it possible the invoice was marked paid when it was entered into the Purchase module?

What does the Vendor Aged Detail report show for this invoice?  Is there a payment under it?

When you double-click the invoice in that report, does it show as paid?

What exactly is happening after you click on the Payment icon?

Any chance there is an error message that might help us help you?

I'm afraid there is not enough information to give you any definitive answer.

"I can't pay" could mean about 4 things off the top of my head. (don't have enough money in the account, can't find the vendor, can't see the invoice when I select the vendor, it won't print a cheque, once completed the cheque won't post)

Is it possible the invoice was marked paid when it was entered into the Purchase module?

What does the Vendor Aged Detail report show for this invoice?  Is there a payment under it?

When you double-click the invoice in that report, does it show as paid?

What exactly is happening after you click on the Payment icon?

Any chance there is an error message that might help us help you?