The PON terminal goes online in an incorrect mode.
The optical fiber connected to the ONT(such as HG8245H) is of poor quality or is loosely connected.
The optical power of the ONT is not within the normal range.
The optical module ages or is damaged under abnormal usage.
The minimum and maximum logical distances configured on the OLTport to which the ONT is connected are inconsistent with the actual distances.
The ONT auto-find function is disabled on the OLT(such as Huawei MA5683T).
When the ONT is added, the configured SN of the ONT is different from the actual ONT SN.
An ONT with the same SN is already connected to the OLT.
The ONT is a rogue ONT.