We saw this issue on 7.1.8 and it was resolved with a local change to pyweb-login-mobile.js TEXT-FILE rule. The solution was also made in the 7.3 version of Pega at the time.
What version are you currently on? For example, if you are on 7.2.2, the code where the local change is needed was modularized out of pyweb-login-mobile and placed in pyWeb-login-mobile-synchronization.
Change is needed in this code :
console.error('ProgressionLoader: Client Store synchronization failed with error ' + status.lastErrorCode + ': ' + status.lastErrorMessage);