@Tài Nguyễn Đức Apologies for the delay in reviewing this post, as per the 1st screenshot shared above, i see only import cycle is being performed for your on-premise connector, to begin with would like to see how many connectors you have in connectors tab, ideally if Azure AD Connect is installed properly, we should have two connectors one for on-premises and other one for Azure AD.
Has anyone made changes to the connectors? Reference: https://medium.com/alexfilipin/azure-ad-connect-dispel-the-fear-33446616de12
Let me know if this information helps to isolate your issue else we can connect offline to troubleshoot the same.
Here are my contact details - send an email on azcommunity [at] microsoft [dot] com referencing this issue with a subject line "ATTN:Givary"
Let me know if you have any further questions, feel free to post back.