Add file type assignment to troubleshooting

Writerside/topics/Installation-guide.md

@@ -30,7 +30,7 @@ In this section we will show you how to install everything that is necessary to
   ![Install](install.png)
 * Install the [PDF Viewer](https://plugins.jetbrains.com/plugin/14494-pdf-viewer) plugin as well, it provides a built-in pdf viewer but does not have full functionality yet. Alternatively, you can install the [SumatraPDF](https://www.sumatrapdfreader.org/download-free-pdf-viewer.html) pdf viewer.
 * If you had to install LaTeX, log out and log back in. Otherwise restarting IntelliJ is sufficient.
-* Click on Create New Project (in the welcome menu) or <ui-path>File | New | Project</ui-path>,
+* If you don't have an open project, click on Create New Project (in the welcome menu) or <ui-path>File | New | Project</ui-path>,
   select LaTeX in the left column and click next. Specify a name for your
   project, and a location. A project can contain multiple LaTeX files and documents, so
   for example if you make a new document for each new homework you get,
@@ -134,7 +134,7 @@ If you have an existing document, you can also use [texliveonfly](https://tex.st
   ![Install](install.png)
 * Also install the PDF Viewer plugin to view the pdf within IntelliJ.
 * If you had to install LaTeX, log out and log back in.
-* Click on Create New Project (in the welcome menu) or <ui-path>File | New | Project</ui-path>,
+* If you don't have an open project, click on Create New Project (in the welcome menu) or <ui-path>File | New | Project</ui-path>,
   select LaTeX in the left column and click next. Specify a name for your
   project, and a location. A project can contain multiple LaTeX files and documents, so
   for example if you make a new document for each new homework you get,
@@ -184,7 +184,7 @@ If you have an existing document, you can also use [texliveonfly](https://tex.st
   ![Install](install.png)
 * Install the PDF Viewer plugin as well to view the pdf inside IntelliJ.
 * If you had to install LaTeX, log out and log back in. Otherwise restarting IntelliJ is sufficient.
-* Click on Create New Project (in the welcome menu) or <ui-path>File | New | Project</ui-path>,
+* If you don't have an open project, click on Create New Project (in the welcome menu) or <ui-path>File | New | Project</ui-path>,
   select LaTeX in the left column and click next. Specify a name for your
   project, and a location. A project can contain multiple LaTeX files, so
   for example if you make a new document for each new homework you get,

Writerside/topics/Troubleshooting.md

@@ -26,6 +26,14 @@ For any performance issue: if you do not have a favourite profiler yet, you can
 * Take a Snapshot to view and save results. Note that you may have to click a few more levels open to see the actual methods.
 * Now you can zip the nps file and upload it here on GitHub.
 
+## I don't see any syntax highlighting
+
+If you have the TeXiFy plugin installed but still don't see any syntax highlighting, you may accidentally have reassigned the `.tex` file type to plain text.
+To undo this, go to <ui-path>Editor | File Types | LaTeX source file</ui-path> and make sure the `*.tex` pattern is there.
+Also check that the Text file type does not have this pattern.
+If the problem only occurs for one specific file, right-click the file and select 'Revert File Type Override'.
+For more information, see [IntelliJ IDEA Help](https://www.jetbrains.com/help/idea/creating-and-registering-file-types.html).
+
 ## Main file is not detected correctly
 
 If TeXiFy does not detect which file is your main/root LaTeX file, you may experience problems like package imports being placed in the wrong file, or imports not being resolved correctly.