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Unfortunately, there is an issue with Huawei "lite" phones that fitbit cannot fix. Thet say:
"Due to Bluetooth issues that prevent Huawei Lite models, including P8 and P9 Lite, from syncing with some devices, like Fitbit devices, our products are not compatible with these mobile phones."
taken from: https://help.fitbit.com/articles/en_US/Help_article/2315/?q=p8
Some people seem to have intermittent success with the phones but others cannot get them to work at all. You could try restarting your fitbit to see if can sync but you will not be able to solve the problem properly. To restart: