As map makers, unfortunately we can't help you to fix issues with Minecraft itself, so the best thing to do is to get in touch with Minecraft support directly! You can follow this link to find the right support: https://minecraft.net/en-us/help/
In the meantime, try some of these troubleshooting options as they may help!
On the main menu, click settings. Go down to storage, where you will see "Cached Data", "Worlds", and "World Templates". Look at each of these. If there is anything relating to the map in question, delete them using the option in that menu. Once this has all been deleted, try re-downloading the map.
If that didn't work, try the following:
Check to see that you have enough storage on your device (the download might be pausing/failing because you don't have enough space)!
If you definitely have enough space for the download, try rebooting the device and retry.
If none of this has worked for you, the best thing to do is to contact Minecraft support directly and they should be able to help you fix any issues: https://minecraft.net/en-us/help/