Added IsRead = 1 to the SET in [pmessage_markread]

UPDATE [{databaseOwner}].[{objectQualifier}UserPMessage] SET [Flags] = [Flags] | 1, IsRead = 1 WHERE UserPMessageID = @UserPMessageID AND IsRead = 0

your DB didn't properly converted (there was a bug in the SQL code which is now fixed). IsRead is no longer a column and is, instead, a calculated field based on [Flags].

can you give a step by step procedure to solve this problem please?

thank you