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Unfortunately there's a specific issue with Huawei's "lite" phones due to their implementation of bluetooth. Fitbit 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