Apparently Ancestry data has some compatibility problems on Gedmstch with other companies, so anyone not with Ancestry has to upload to their Genesis Project. However, you, being with Ancestry, can upload to Genesis whereas people with the other companies cannot go the other way! They are planning to migrate everyone to Genesis in the future.
So if you want to match with 23 and me or Living DNA people go to Gedmatch home page. You will see a series of blue coloured text boxes.
Make sure you have your data downloaded from Ancestry and saved in a file where you can easily find it.
At the homepage, go to the lowest blue box
Click on "find out more about genesis beta"
On next page click on "click here to continue to Genesis home page"
You will now need to input your email and password again
Follow intstructions to upload your data
On the left hand side your name will be in colour.
It will change as the download progresses to orange, light green then dark green
When it is dark green you are ready to compare with other people
You will have a new number which is different from your Ancestry number, but you can use this to compare to people on Genesis and the original number to compare as you do now with Ancestry people.