Issue with dual charging iPhone and iPad

Hi. I bought an Anker 24W dual port charger (with “PowerIQ”) with the idea that I can charge my iPhone 8 and iPad 2018 when travelling. However, charging the iPhone and iPad together did not work at all. The iPad stopped charging, started to bleep, etc, when both iPhone and iPad were connected to the charger. Is this a known issue? Are there other options from Anker products that work better with dual charging current Apple devices, with at least 2 or maybe 3 usb ports? Also, I live in Europe where we often have the plug that is not supported by many Anker products available online.