
Also in the Google Chromium when I see the code of the app, there is an error related to this error message.

So I build completely fresh Moodle servers (Moodle 2.8.5, Moodle 2.8.7 and Moodle 2.9.1) separately from my institution Moodle server, without any plugins or any themes. I download the Moodle mobile 2.0 from apple store for iOS device. I also use the android branch of Github repository link of moodlehq/moodlemobile-phonegapbuild (https://github.com/moodlehq/moodlemobile-phonegapbuild.git) and convert the app through Phonegap build online tool for android device. (The way I convert the Github repository link to an app can be seen at the end of the message.)
On Moodle 2.8.5 and 2.8.7, both iOS and Android devices have the same error messages as I mentioned above. On Moodle 2.9.1, both of the devices work fine, with no error message. It seems this error message only appears on Moodle 2.8.
Currently, my institution uses Moodle 2.8.7. Since folder activity is a basic activity in Moodle, many teachers are using this activity to organise their lecture resources. This error message issue really influences the behaviour of the Moodle mobile in my institution. In addition, this is the first time we introduces Moodle mobile to staff and students. As a result, it is very important to leave a good impression about this mobile app to users. Obviously, this error message is quite a big problem. I would be grateful if someone in Moodle mobile development could help to solve this issue as soon as possible.
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The way I use to convert the app is:
First, get the link of moodlehq/moodlemobile-phonegapbuild in Github (https://github.com/moodlehq/moodlemobile-phonegapbuild), and choose ‘android’ branch. Then copy the URL of the page on the right hand side of the page.

Then, in the phonegap build, I paste the URL and branch in the form. Then Phonegap Build convert the app online.
The app I convert is here: https://build.phonegap.com/apps/1630284/builds
