I already answered on SO, but I will add the answer here as well, maybe someone will encounter similar problem.

In case of any further problems with MDB its better to use our support forum, because you will get a much faster response here than on SO.

Lazy loaded modules in Angular can be loaded on demand and are not included in the global scope of you app. That's why when you use lazy loading, you should import MDB modules to every lazy loaded module.

Here is a list of all MDB Modules: https://mdbootstrap.com/docs/angular/getting-started/modules/

'MDBBootstrapModulesPro.forRoot() - contains all MDB modules, but you will probably want to import only single modules like 'ButtonsModule' to your specific lazy loaded module.