I updated the app from 2.24 on my HTC Desire and found that I lost my notifications to my Blaze. I did the re-start to re-enable notifications after installing as instructed. They worked for a few hours then stopped completely, I think it may have tied in with when the phone connected to the cars Bluetooth simultaneously, prior to the update I had no issues with this.
I managed to get them working again the following evening by unpairing my Blaze from the phone, disabling notifications, re-starting both the phone and Blaze. I then re-enabled notifications, paired the tracker to the phone and found I could get notifications again.
Just for clarity, the notifications were not received when connected to just the phone not only when connected to car and phone at the same time.
I lost them again the following day, not sure when they went but i suspect it may have been after the phone connected to the cars Bluetooth again.
As I had not had this issue before I suspected the latest update, so uninstalled the version 2.25 Fitbit app reinstalled version 2.24. This has now been back on the phone since Friday 20th with no issues and will once again receive notifications on the Blaze at all times including whilst connected to the cars Bluetooth as well.
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! I'd recommend taking a look at the troubleshooting steps I share here in order to solve the issue with the call notifications. 
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