Things also tend to get wonky when there's not enough room on the hard drive.
Tried a different computer with the same result so I doubt it's a problem on my end.
I've been getting that error too. Unable to run missions for the past two days..
Use the mobile version if you're in a hurry. It seems to work just fine.
Name: Volarmis
DMM ID: 317568967
I got that 'loading failed' error as well. Skip tickets still work though so that's one way around the error while still being able to finish event and daily missions.
Nutaku and DMM IGN: Tomitain
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Nutaku Flower Knight Girl ID: 610834201 (inactive)
DMM FKG ID: 106750967
DMM FKG Allies: 109/123
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DMM Girls Symphony ID: 34644951 (inactive)
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Nutaku Mist Train Girls ID: 3355988
DMM MTG ID: MSTL0Q45K5E9
MTG Allies: 31/50 (Nutaku), 11/50 (DMM)