When you mention you can only able to see 43 available services, are you talking about a Neo trial account or a Cloud foundry trial account?
We are currently only supporting deployment to SAP cloud foundry.
you could check this by checking whether your region is one of the following:
Europe (Frankfurt), US Central (IA) Beta, US East (VA), US West (CA) Beta
if your trial account region is not any of the following then you're running your trial account on the Neo environment of SAP.
Thanks for trying the Mendix demo for SAP. The quota message is given when any of the limitations are reached, typically for a trial account the limit is 10 services of which one is a database. This means besides deployed apps you can check the created services on the SAP Cloud Platform Cockpit.
To do this navigate to the space and check the Service Instances (left menu). Delete any unbound service to free your resource. An overview of used resources is available on the sub account overview page in the cockpit.