The transponders issued over 5 years ago are nearing their end of life where the non-replaceable internal battery dies. The club will gradually replace transponders as they fail at a cost of $77 to the member and these should last another 5 years. If your old transponder is not detected in a race finish (as indicated in the published results), please return it to the club for checking, it may be due for replacement.
The transponders are somewhat sensitive to their placement on the bike. In particular, covering the outside with the velcro fastening strap may affect the functioning. A rule of thumb is to try to maintain a clear line-of-sight between the outside surface of the transponder and the detecting hardware at the finish line.
Example of correct method of attachment:-