Tearing My Hair Out

[CordeliaEarle]

Hope someone can tell me what I am doing wrong.

I have copied and pasted from this web page: https://www.mrexcel.com/news/next-invoice-number/

and have corrected all the cell numbers to do with my saving details, and the macro is perfect. BUT, when I then go in to the invoices again, to invoice some more at the end of the next month I always get the following error:

https://picmonkey.space/invite/36vRandbvJwPbDV5YoJPpW

Please tell me why this happens.

 

[CordeliaEarle]

Tried it on a different invoice, comes up with this

 

[Fluff]

Are you getting the same error message, or a different one?