Personally, I would suggest not using that app. It doesn't do well/work well. Now to try and get it working again...
Did you try restarting (turning off and back on) the phone? That would be the first thing to try.
Should that not resolve it, then I would ask if you recently installed anything that could be interfering with the app? If so try uninstalling whatever it was, and then again restart the phone.
If nothing was installed, or uninstalling something that was installed turns out to not be the problem, then I would see if there are any updates you need for the app.
Next I would try uninstalling the app, restarting the phone, and then reinstalling the app. Not just deleting the icon but completely removing it, restarting the phone and then redownload and install it.
If all the above fails to resolve it, then you need to contact the apps creators about the app itself.