Cannot connect to SQL Server

Question

Handian Sudianto 7,141

Let say i have server A and two sql server, SQL1 and SQL2.

When Server A try connect to SQL1 then i got below error from SSMS, but if connect to SQL2 then the conneciton is working fine.

Other servers beside Server A can connect to both SQL. A

Anyone know why? User's image

Viorel 126.9K Reputation points

2026-02-10T02:54:27.0866667+00:00

It would probably helpful to indicate all versions.

It seems that the search result provides solutions related to the so-called TLS.
Erland Sommarskog 134.2K Reputation points MVP Volunteer Moderator

2026-02-10T21:58:46.1533333+00:00

I echo what Viorel says. Please post the output of "SELECT @@version" from the two SQL Server instances. Please also tell us the OS versions of all three machines.

Answer recommended by moderator

0 additional answers

Viorel 126.9K Reputation points

2026-02-10T02:54:27.0866667+00:00

It would probably helpful to indicate all versions.

It seems that the search result provides solutions related to the so-called TLS.
Erland Sommarskog 134.2K Reputation points MVP Volunteer Moderator

2026-02-10T21:58:46.1533333+00:00

I echo what Viorel says. Please post the output of "SELECT @@version" from the two SQL Server instances. Please also tell us the OS versions of all three machines.

Answer 1

This error, the client and server cannot communicate, because they do not possess a common algorithm, is almost always a TLS version mismatch.

Since:

The issue is very likely that SQL1 does not support TLS 1.2, while Server A has older TLS versions (1.0/1.1) disabled.

2. If it’s an older build (SQL 2008 / 2012 / early 2014), install the latest Service Pack / CU.

3. Restart SQL Services and test again.

Updating SQL1 to a build that supports TLS 1.2 resolves this issue in most cases.

Thanks,
Akhil.