Thank you for your response!
This does not address this issue however as I have created tables via the Advanced Table block were I was able to merge cells. I am no longer able to though when creating new advanced tables OR when going back into tables I previously created that have merged cells.
For the previous tables, I can select the merge cell block and it gives me the option to “Split merged cells”, but I cannot merge any new ones.
Why is this and how do we fix?