Hi any suggestions?:
1998 Buick Century 3.1 105,000 miles. Factory keyless entry, anti theft chip in ignition key, no alarm system.
Owned the car for a year now, came with one key fob. I bought a second new key fob on ebay, right after I got the car. It looks just the same as the other one and synched and both key fobs have been working just great with the vehicle.
Now recently recently the car battery needed replacement, put a new battery in.
Shortly after, both key fobs stopped working at all or intermittently and when working required very close proximity to the car.

Replaced both key fob batteries and cleaned all contacts in key fobs with a damp rag and reassembled. No change.

Re-synched both key fobs to car, using both the technique of holding unlock door button on driver's door while pressing unlock lock buttons on key fob one at a time till chirps are heard. Also then tried the place key in ignition three times and pressing both unlock lock key fob buttons till chirps heard. Chirps confirmed ok but key fobs still not working most of the time. It's like the pickup antenna on the car is broken or ....a corroded fuse or...

Any ideas to try? thanks