The flashing E means that the film has no more exposures left. When this
occurs the film is usually automatically rewound into the cassette and
the loading door can then be opened.
In your case, the film has not fully rewound and so the door remains
locked. A fresh battery usually cures it but has not done so in your case. You can try using a pointed object such as a pen or pencil to press the manual rewind button on top of the camera (below the "select" and "enter" buttons on the top plate) but if that fails then you will need to break open the camera in total darkness to remove and rewind the film.
Breaking the camera seems drastic, but if the camera is broken then it's effectively irreparable anyway. APS cameras were a very badly engineered system and there are very few which are still working these days as the film transport mechanism was simply awful. There were various other problems with them as well, so many don't work for other reasons.
After you recover your film you can either replace the camera with another one (APS film is an almost dead format though) or switch to a conventional 35mm film camera which has better image quality as well due to the larger negatives. Either way, there is absolutely no need to actually pay for one; there are millions of them sitting unused in people's drawers and cupboards and you can either wait for one to be offered on your local FreeCycle/Freegle groups or request one. Note that a rule of these groups is that your first posting MUST be to make an offer, but you're free to respond to offers for items offered by other members.
You might want to consult this online resource from Kodak
regarding your camera for further information about it.
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