why are tables missing from information_schema.tables in MS SQL database?

They are system tables.  Look in the Tables | System Tables node.

Can I delete them from information_schema.tables?
No.  That is a system VIEW.

Or is there a way  refresh information_schema.tables so that it is correct?
I suspect you will find it is correct.

Incidentally the information_schema is practically deprecated.  You would be better off using sys.Tables instead.

sys.tables still shows several tables that are not listed when I open the database in SSMS and expand the tables node. Also, when I try to run a re-indexing script that selects all of the tables  from the sys,tables or information_schema.tables, I get an error when it can't find the tables that show up in sys.tables but do not show up in SSMS. My assumption is that the tables had been deleted a while back.

When you say;

Or is there a way  refresh information_schema.tables so that it is correct?
I suspect you will find it is correct.

Are you saying that the sys.tables or information_schema.tables is correct, but SSMS is not showing all of the tables in the database? I am logging in as the SA

Thanks,

Dave

sys.tables still shows several tables that are not listed when I open the database in SSMS and expand the tables node
As I stated they could be system tables or simply that you have not refreshed the tables node in SSMS.

Are you saying that the sys.tables or information_schema.tables is correct
Yes.

The problem is that I can tell by the table names that they are related to the project that the database is for.

I have refreshed the SSMS, logged in and out. Those tables are just not available via SSMS or evn SQL Query. For example, I can just do a Select * from tablename and I get an "invalid object name" error.

That was it. They had different schema and so were showing up in SSMS with the schema first. Thanks for all your help.