Looking at this screenshot, your email address is linked to two accounts. This is where you see options to select an account when accessing Mobile services cockpit in browser. This UI window is currently not available in VSC, hence, you can't pick an account while deploying MDK metadata to your mobile services. We'll enhance this in future.
Are those both accounts are S-user and P-user? When you deployed from VSC, did you provide the email address linked to your universal ID OR P/S-user ID? It should work with user ID (i tested with my Universal Id which has two accounts linked to it, deployment works fine when providing my P-user instead of email address).
You can of course continue your development if above works for you. However, i suggest you using MDK tools CLI to deploy your metadata to mobile services. Once you have the BTP org and space set, you don't need to enter credentials anymore.
Please do the following:
as a workaround: you can do the deployment manually. Inside the settings of MDK plugin, you find
Mdk: Create Upload Bundle Zip
Please check the relevant checkbox. While building on a mac, you find a file called uploadBundle.zip a the following location:
The correct location is shown at the end of your build process in vscode as well.
So open the update section inside your app on mobile service in BTP and upload this file. Deploy it and it will be available for all users.
This gives you more control, as you can store these ZIP files as versions in GIT and you can deploy the same file on all instances.
Hope that helps.