I use PS ImageReady for gif animation, I'm only just starting out, but to create an animation you must 'tween' (transitions) all the images in your animation.
If I was to open your gif in PS Imageready would I see multiple frames of the gif? I think not. To edit the gif I'm sure that you must have the original image/images, then add your text/changes and then tween the animation.
It is likely that after you added the text to your animation it has messed up the animation and changed it to a standard image.
Sorry if that's not much help, but I'm sure this is the problem.
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