As long as you don't sign-out, you should only need to sign-in once and the app will keep you signed in. If the app keeps requesting a sign-in, can you please send an e-mail to firstname.lastname@example.org and we'll work with you to resolve the issue.
thx for the reply but of cause I am not so silly as to sign out deliberately in fact I didn't sign out at all unless you consider my action listed below as signing out?
i was working on something offline and I happen to click on the blue square icon on the top left corner to check if there is a user guide and next thing I know it request for me to sign in again.
It was not our intention to require a consistent network connection. You should have only needed a network connection on your first sign in. Once you are signed in, you should have been able to work offline indefinitely.
Unfortunately, the app has a bug which causes the app to sign the user out in certain situations, and we did not catch this issue prior to release. We have tracked down the issue, and we have a fix in place which will be included in an upcoming release.
Sorry for the inconvenience.
We recently posted an update to Sketch on the App Store that should solve the issue you're having with the app logging out. Please update to this version and let us know if you're still seeing the issue.