As of MemSQL Studio version 2.0.0, which will be the next release (planned for August 21, 2020), Studio will not be compatible with the MemSQL Engine version of 6.5.
If you are currently running MemSQL 6.5, you can continue to use older versions of Studio. However, to use Studio 2.0.0+, you must upgrade to the MemSQL engine version 6.7 or higher. MemSQL Studio will continue to be compatible with MemSQL engine versions of 6.7 and higher.
Note that outside of Studio compatibility, MemSQL version 6.5 has reached its end-of-life, so it is recommended you upgrade to a newer version.