Issues accessing the Spanish ING Direct app

Having trouble accessing the ING Direct app?
Since September 2019, the app kept giving me errors, even though I correctly completed the mobile-phone verification and made sure the app was up to date. I eventually found a fix by chance: once I cleared the app’s temporary files, it worked perfectly.

Follow these steps (may vary by device/brand):
Settings > Apps > Storage > Clear data.
Then, on the same settings screen, also clear the cache: Clear cache.