Excel won't save new workbook

[cryptogram]

Excel (2003) won't save a new workbook, only existing ones. Why would that be? This has only happened since I upgraded to W10.

[candybg]

Where is it saving the new file?
Path - directory - folder?

[cryptogram]

That's the problem. 'Save as' does not open a dialog box. Nothing at all happens. But it does if I try to save an existing file.

[candybg]

On a new file, you normally don't use SAVE AS, just SAVE.
The dialog box that opens should show you WHERE the file will be saved. That might be the issue - or maybe not - but lets start there to see if we can isolate the problem step.

[cryptogram]

Rightly or wrongly I always use 'save as' for a new file. But if I use 'save' it still opens the 'save as' dialog. Anyway, right now, nothing happens, so I can't save it anywhere.

Subsequent editing - -
But now something has changed!! Saving works. Thanks for your thoughts so far.