Visualizations disappear when reopenning

Question

Data is reloaded when I reopen the QGIS, however all of the visualizations disappear when I reopen the QGIS. I add the dataset as follows:

Visualization looks as follows:

When I reopen the QGIS, it looks like this:

Data is there, here is the attribute table:

I am very new at QGIS and not sure why exactly this occurs and wanted to give as much as clues I can. In the past, when I reopen the QGIS the visualization was done automatically, I wouldn't have to do it all again. But like this, it causes so much waste of time.

Answer 1

The problem

Field delimiters are not correctly recognized, see your last screenshot: all attributes are in one single field. Semicolons should work as delimiters, but are not recognized as such.

The solution

In the import dialog, instead of Regular expression delimiter check the box next to Custom delimiters and select the semicolon ;

Context

As you can see on the 3rd screenshot, the CSV is loaded without geometry, so there is just attribute data. Your 2nd screeshot shows the symbolization icons, whereas in screenshot no 3, there is just the list icon (data only layer).

Check Data Source

If you open the project, in the Layer Properties > General Tab you can see the data's source. See below how it looks in my case and check how it looks in your case - especially the delimiter=; part as well as xField and yField parts. The first part (C:/Users/[username/folder]/temp/) is just the local drive where I stored the data and probably looks different in your case:

soucrce:

file:///C:/Users/[username/folder]/temp/demand_1.csv?type=csv&delimiter=;&quote=&escape=&maxFields=10000&detectTypes=yes&xField=DemandLat&yField=DemandLong&crs=EPSG:4326&spatialIndex=no&subsetIndex=no&watchFile=no

Provider delimitedtext

Answer 2

Short answer

Avoid special characters for folder and file names. Use only letters, numbers and underscores, then the problem is solved.

Details

I could now finally reproduce the behaviour you describe. The problem is the path you use for the csv file: it contains special characters. Your first screenshot shows the path where you saved the csv. This path contains different special characters like points (.), spaces ( ), commas (,), hash sign (#), hyphens (-) apostrophe ('), equal sign (=) etc. This should be avoided.

Using such characters might work in many settings. However, it might suddenly produce unexpected errors, as in your case. So as a general rule (not just for QGIS), always limit names for folders and files to characters a to z and A to Z, numbers 0 to 9 and underscores (_) and avoid all other characters.

Depending on context (operating system, file system, filetype, application used etc.), rules for allowed/forbidden characters vary - see e.g. naming conventions for web files. In some contexts, filenames are not case sensitive, so you might even consider using only lowercase (or only uppercase) characters or only hyphens instead of underscores. For maximum interoperability, keep file- and foldernames as simple as possible and as complex as necessary. See also entry for Filename on Wikipedia.

Checking data source in Layer Properties > Information reveals the problem: path includes special characters like hash sign, spaces and hyphens, all data are inserted in one field and thus the fields that define the geometry cannot be recognized: