Here is a link to the Ifixit teardown for your phone.
In Step 7. of the teardown it mentions ''flat antenna cables'', just after removing the battery. Perhaps you loosened their connections when you removed the battery.
[guide|27458]
Hopefully this is of some help.
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=== Update (02/03/2017) ===
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Hi,
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Here is an image showing the actual connectors. Check that they are both OK. [image|1014343] (Click on image to enlarge for better viewing)
Hi,
Here is a link to the Ifixit teardown for your phone.
In Step 7. of the teardown it mentions ''flat antenna cables'', just after removing the battery. Perhaps you loosened their connections when you removed the battery.
[guide|27458]
Hopefully this is of some help.