Numbers 5.2 no longer indexes cell content

After upgrading to Numbers 5.2, noticed I can no longer search newly created spreadsheets by content. I'm referring to pressing command O (open) within a spreadsheet, then command F (find), keying a search character string.

Old spreadsheets created with the previous version of Numbers are still searchable by cell content (in this case, daily dietary spreadsheets, containing text entries indicating different foods, such as Sunflower Kernels, Salmon, Burrito).

Have tried rebuilding spotlight indexes, and upgrading to new version of MacOS, thinking perhaps indexing for Numbers 5.2 required Mojave. Condition persists (old spreadsheets are searchable by content, but not those created by Numbers 5.2). Is anyone else seeing similar search behavior? Is there perhaps a list of known issues with Numbers 5.2? Maybe the feature has intentionally been removed for Numbers 5.2 spreadsheets? Maybe there is some maximum number of cells within spreadsheets that can be indexed?