Place a single pixel in bitmap mode? Photoshop says no.

The issue appears to be fixed in the just released Photoshop 2024 25.4 update.

Reproduced in Sonoma 14.3, Photoshop 25.3.1. Pencil, brush tool, and Edit->Fill bring up Program Error dialog for bitmap documents. Interestingly, Invert works and then a white pencil is fine, either on black or when inverted again, on white. Switching back to black pencil gives the error again.

Yes for me macOS Ventura and Sonoma have the error with photoshop 2024 (ps ver 25.3.1) but not macOS Monterey.

https://community.adobe.com/t5/photoshop-ecosystem-discussions/why-can-t-i-paint-in-a-1bit-bmp-canvas/m-p/14305067

Until it gets fixed you could install Photoshop 2023 (ps ver 24.7.2) which does not have this issue.

Go to

/Applications/Adobe Creative Cloud/Adobe Creative Cloud

then where you see Photoshop under All apps, click the three little dots to the right of Open and click Other versions.

No problem, or error, doing that here, in Photoshop v25.3.1 on Windows 11

May be an issue with Sonoma - perhaps a current Mac user can confirm.

Dave