I found that Brooklyn is a little less forgiving in query strings and conditions when typos are made - previously they may have worked.

Can you double check this string:

The Query string i have on my page include properties is id={{$Param.id}}&accId={{$Model.Entitement.data.0.AccountId}} 

I noticed your model name is Entitlement spelled wrong.  Does it match your model name?

Also make sure AccountId is included in your Entitlement model.

Other thing I would check is case sensitivity of your url parameters… are they really ‘id’ not ‘Id’ and ‘accId’ not ‘accid’ and things like that.

Related to that, check your model conditions to make sure the case is exactly the same as the query string.

So bottom line, make sure all the fields you are using to query or pass to other queries are included in your model(s), and your spelling is perfect on case.

There is no issue with model name. I have model name as Entitement.

Also the query string and other conditions that i have are on the Account and Entitlement fields. These fields are showing data properly. the problem is contacts data is not being displayed. This is the error i am getting when i try to look for contacts;

An error occurred while attempting to perform the following SOQL query: SELECT AccountId,Account.Name,Account.Id,AssistantName,Name,Id FROM Contact WHERE ((Account.Id = ‘T_Deloitte’)) LIMIT 10000 Error:invalid ID field: T_Deloitte.

So the Account.Id condition is looking for a true Salesforce ID (18 digit) but instead it is getting passed some text, T_Deloitte.

On your contact lookup field settings, Filter tab…

Change your lookup fiber from Account.Id to just Account.

From this:

To this (don’t click through the account ref to the ID field):

See if that works!