There are two things you should try:

1.) Reflashing the ROM
2.) Go to Settings>About Phone>Check for Update

 

verizon stopped pushing the OTA to eris phones. you will not be prompted for any system update.

 

try this [ROM][10/20/2010]FlashBack21 v1 -Return to Factory Stock - UPDATED - xda-developers

 

Correct.

This is also correct; it updates to the July 2010 software but does not rely on OTAs - but you will need to re-root before you can install it.

I think you will find that the "One Click" rooting method does not work with Android 1.5 on the Eris - but the "Dummies" method does. Or, if you are familiar with using PB00IMG.zip or RUU methods, you could flash your phone to any of the 2.1 (leak) releases, and then root from there if you want to use "One-Click" instead of "Dummies".

Good luck; let us know how things work out for you.

eu1

 

The Flashback21 ROM also will unroot your phone. It is the replacement for the Flashback15 ROM - and so it is also intended to return your phone to a factory state.

I mentioned the other two methods of converting to 2.1 (prior to rooting) only if you were already familiar with them; since you are not, I would suggest you ignore that comment, and just root your phone in its' current state (1.5) by using the "Universal Root for Dummies" method.

After that step is complete you can then apply the Flashback21 ROM to unroot your phone.
eu1