can't alter table to create index

[Anthony Esposito]

AWS RDS MySQL 5.6.35

When attempting to create an index with the following SQL

ALTER TABLE `mytable` ADD INDEX `ix_myindex` USING BTREE(`columnID`);

the command never returns or creates the index nor gives an error.

The table in question has 6000 rows.

What could be the issue? Where can I look for error messages?

In the AWS console I have looked at the error log but it says IP address / resource not resolved. However, I do not get an error to the command-line mysql client nor via MySQL Workbench.