iOS 15 is not installing on my iPhone SE

You are right, veena293! That is a completely unhelpful error message!

I see that you have a good charge on your battery, your iPhone isn’t in Low-Power mode, and that you are connected to Wi-Fi.

It can help to have your iPhone plugged in, while you are downloading and installing an update.

However, there is another issue that can cause an issue with installing an update: you may be running low on available storage (may need about 15GB of Available storage, before the download).

Sometimes, this issue will be signified by an error message stating that there wasn’t enough Storage, but, unfortunately, that isn’t always the case.

Whether Storage is the issue or not, another way around this update issue is to plug your iPhone into a Computer (PC running iTunes, or a Mac using iTunes or the Finder, depending upon the macOS version), in order to perform the update.

Welcome, veena293, to Apple Support Communities!

What ERROR are you getting when you try to upgrade your iPhone SE?

(A screenshot could help.)

veena293 wrote:

Thanks. I will try on computer.

Feel free to let us know how that goes, and if you need any further assistance, such as with the computer assisted update!