Editing attribute cell data/text in "edit" mode using QGIS

I am using QGIS3.4.

I turn my layer on "edit" mode. I want to type text into a blank cell or paste text. I don’t know why it will not allow me to enter anything while the layer is in "edit" mode. I have been able to do this in the past.

I am fairly new to QGIS so some of the following answers might not make sense due to my lack of knowledge but here we go. I think I may already know what is wrong but I am answering the questions fully to assist other users like me in the future and also I do not fully understand GIS as a whole at this point.

My layers are from multiple origins. Some layers are shapefiles (via zip files downloads) from my local government agency website. The layers that I am trying to edit are shapefiles created internally from a previous a software called UDIG.

I am not sure I understand the difference between a file or a database. I imported shapefiles into a new QGIS project. Then I saved the QGIS project to my local drive. From there, I downloaded the QGIS Cloud plugin to create some online maps.

At first, the file was saved locally on my drive. After using the QGIS Cloud plugin, I believe the file/database is stored basically on QGIS Cloud. I have lost some data and had problems not knowing how QGIS cloud is handling my data.

I think the file type is all Shapefiles. I really couldn’t explain the differences in each of a Shapefile, a Geopackage, a PostGIS database, a WMS connection etc. I need to read more on this. I assume Shapefiles and Geopackage files are basically the same but store my vector data a little different. I don’t know really anything about a WMS connection yet but I assume it is a way to connect remotely to a database of information without storing the information on my computer. Basically, I open the QGIS file and it opens the WMS connection.

I have included a screenshot of what I am trying to do.

I have included a screenshot of my layer properties / Information tab to show the source of the layer.