After update to v29, when making an album, the error message "metadata is read only" appears.
I tried to re-install the previous version of Jalbum, but that didn't help. The same error message appeared.
Then I tried to install version V29 again. I still cannot generate any album due to the same error. In addition, another errror appeared. The appearance of "Jalbum Dark" that I used to have, no longer works. I can tick it in Settings-Preferences and then restart jAlbum, but does not have an effect.
How to solve this?

Thanks for the suggestion. My first question is answered. I can now generate albums again.

The other question is not yet solved. jAlbum always shows the grey appearance, as shown in the screenshot. Instructing jAlbum to display another appearance (and restarting jAlbum) does not change anything.

I've never seen that behavior actually. Try opening Tools->Open directories->Config directory and delete the "defaults.jap" file, but do the deletion when jAlbum isn't running. Now start jAlbum again. it should now be set to "factory defaults"

Please edit defaults.jap in a text editor and ensure that the "lookAndFeelName" property looks like this:

lookAndFeelName=One Dark

Save and start jAlbum.

If it still is ignored, look for any triangle in the lower right corner of jAlbum, or try running jAlbum via a startup script. That can reveal some deep problem early during the startup.

I have looked in the tutorials and found instructions that made me try to do the following: first I opened a cmd-window; then I issued this command:

java -jar "c:\Program Files\jAlbum\JAlbum.jar"  "f:\Photo\Jalbum-instellingen\settings_bestanden\testalbum.jap"

The output was as follows:

Could not load look&feel One Dark 
java.lang.NoSuchMethodError: java.awt.Toolkit.getMenuShortcutKeyMaskEx()I
        at se.datadosen.component.SmartTextComponentSupport.<clinit>(SmartTextComponentSupport.java:52)
        at se.datadosen.component.SmartTextComponent.makeSmart(SmartTextComponent.java:53)
        at se.datadosen.component.JSmartTextField.<init>(JSmartTextField.java:23)
        at se.datadosen.component.JBackgroundTextField.<init>(JBackgroundTextField.java:37)
        at se.datadosen.component.JDatePatternComboBox$DatePatternComboBoxEditor$1.<init>(JDatePatternComboBox.java:33)
        at se.datadosen.component.JDatePatternComboBox$DatePatternComboBoxEditor.createEditorComponent(JDatePatternComboBox.java:33)
        at javax.swing.plaf.basic.BasicComboBoxEditor.<init>(Unknown Source)
        at se.datadosen.component.JDatePatternComboBox$DatePatternComboBoxEditor.<init>(JDatePatternComboBox.java:29)
        at se.datadosen.component.JDatePatternComboBox$DatePatternComboBoxEditor.<init>(JDatePatternComboBox.java:29)
        at se.datadosen.component.JDatePatternComboBox.<init>(JDatePatternComboBox.java:21)
        at se.datadosen.component.JDatePatternComboBox.<init>(JDatePatternComboBox.java:16)
        at se.datadosen.jalbum.JPreferencesWindow.<init>(JPreferencesWindow.java:156)
        at se.datadosen.jalbum.JAlbumFrame.<init>(JAlbumFrame.java:177)
        at se.datadosen.jalbum.JAlbum.<init>(JAlbum.java:137)
        at se.datadosen.jalbum.JAlbum.main(JAlbum.java:388)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
        at java.lang.reflect.Method.invoke(Unknown Source)
        at se.datadosen.jalbum.Main.main(Main.java:45) 

Mark the first line of output . Does this give a clue, perhaps?

Strange. I have re-installed java and checked its versions by:

C:\>java -version
java version "1.8.0_341"
Java(TM) SE Runtime Environment (build 1.8.0_341-b10)
Java HotSpot(TM) Client VM (build 25.341-b10, mixed mode)

Should this java version work? because unfortunately, it doesn't.

Thanks. I have completely uninstalled jAlbum, and then re-installed it again. Now it works properly, fortunately. Thanks again for the help. Case closed, as far I'm concerned.