If you are entering right password and unable to login then first check that in Keyboard Caps lock that should not be On
if still facing issue then follow the below mentioned steps:
Step 1: Go to system's Control panel
Step 2: Click on Regional setting and change the format as United Kingdom
Step 3: Chanage Locale and then click on Chnage system locale
Step 4: Untick the option Beta-use Unicode UTF-8 for world wide language support
Yes, there is a mobile app availble for BUSY, You need to take subscription to use mobile app.
In BUSY mobile app you can view 100 reports sales, purchase, receivable, payable, stock statusetc.and can create and share invoices from mobile app.