Conda create with python version fails me

About two years ago I moved from pip to conda. I have been happy with
conda until yesterday.

I want to create a new environment using a specific python version 
rather than leaving that to conda. Cheat-sheets and online conda
documentation tell me to use:

conda create -n <name> python=<version number>

like:

conda create -n test python=3.10

Which in my case yields an error message saying python 3.10 is not
available in this environment.

I have tried variations on the python specification:

python==3.10.12
python=3.10.12

To no avail.

I think (!??!) I have managed to do this in the past.

Any help is more than welcome.

/Martin