TablePress Extension: Rowspans everywhere
TablePress plugin caches the table markup (as transients).
If the table markup doesn't change after installing/updating this plugin,
the TablePress cache may has to be invalidated.
Either delete the TablePress-related transients,
all transients (as transients should only be used for temporary data),
or update the cache by re-saving the tables that should use
this plugin by using the outside_rowspan trigger word.