In SharePoint 2019, after applying KB5002639 and subsequent updates, deploying BCS solutions is not possible.

Hi @seungjae lee ,

Welcome to Q&A forum!

I have done a lot of research, but there is not much reference material for your situation. Based on the information you provided, it can be determined that it is caused by an update, but the recent updates do not specify the impact on BCS. You can check if there are any Windows updates that have not been installed, which sometimes has an impact. If it doesn't work, you can try to roll back the update or wait for the next update to see if it can solve the problem. However, the forum engineer has limited authority. If you need to roll back the update, you need to escalate the issue. You need to contact Microsoft directly to operate. The support team over there has the correct escalation channels, and they can devote more resources and investigate the behavior from the backend as quickly as possible. They can also remotely check the behavior on your side. They can even help you find the root cause of the issue. For reference: Global customer service phone numbers. This is the most efficient way to handle this thread given the circumstances. I'm confident that our expert engineers over there can resolve this issue efficiently and accurately.

Good day! Happy New Year to you in advance!

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