I want to get the new iOS15 update

The message states “at least 1.83 GB”, so you’ll seemingly some need more free storage here. You’ll either need to free up more storage, or update using a Mac or Windows computer. Having 2GB free is “full”, too; not enough room for anything else that might happen, and performance can suffer here.

You are not meeting all the requirements. You need to have at least a 50% charge, better yet, leave it plugged into the charger while updating. You also need to turn of Low Power Mode. And you need at least 6 gigs of free space.

Make sure you:

• Are using a WiFi connection (not a hotspot).

• Have your battery charged at least 50%. Better yet, keep it plugged in during the update.

• Are not using a VPN connection.

• Do not have power save mode turned on.

• Do not have a beta version installed.

• You have at least 6 gigs of storage available.

You can also check out this article for help -

If your iPhone, iPad or iPod touch won’t update

https://support.apple.com/en-gb/HT201435