[Solved]-Model class doesn't declare an explicit app_label and isn't in an application in INSTALLED_APPS

My solution was to create a BaseModel abstract class on your models.py within your app, on your error this may be:

class BaseModel(models.Model):

    class Meta:
        abstract = True  # specify this model as an Abstract Model
        app_label = 'wdland'

And made all models inherit from this instead of the usual models.Model.

To solve it, I went to the basics of trying to figure out the error message, which states:

Model class wdland.models.Device doesn’t declare an explicit app_label and isn’t in an application in INSTALLED_APPS.

I also had the same error with a different app. Adding the requested “app_label” solved the issue.

Just adding "app name" to the installed apps in the settings file.
In my case the "app name" is proteins and my installed apps look like this

INSTALLED_APPS = [
'rest_framework',
'proteins',
# 'proteins.apps.ProteinsConfig',
'django.contrib.admin',
'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.messages',
'django.contrib.staticfiles',

]

I think you don’t have django.contrib.contenttypes this in INSTALLED_APPS of django settings.So add it in INSTALLED_APPS of django settings