My Invoice serial is not automatically changing ..it working earlier, but How i dont know it got fixed and not changing the invoice no automatically,

Hi @glarysolutions,

I'll share with you some things you can do when you encounter unusual situations in QuickBooks Online (QBO).

The first thing to try is to open your browser's private window. It isolates the cache, which is the common cause of unusual behaviors in browsers.

• Google Chrome: Ctrl + Shift + N
• Microsoft Edge: Ctrl + Shift + P
• Firefox: Ctrl + Shift + P
• Safari: Command + Shift + N

If that works for you, go back to your regular browser and clear its cache. Otherwise, open an alternative browser that's available for you. 

On the same note for your invoices, see this article: Import custom form styles for invoices or estimates. It's a detailed guide on how you can generate a custom template, which you can then upload to your QBO company.

Feel free to post a comment below if you need further assistance on this matter. I'll get back to you as soon as I can.