Hello,
Below is the valition rule which i have created. The requirement- whenever the stage is set to as 'Closed Lost' , the loss reason need to be mandatory for the different record types mentioned in the rule. 
The rule is not getting triggered and i am able to save opportunity without prompt of the error
Please advice

AND
(ISPICKVAL(StageName, "Closed Lost"),OR ($RecordType.Name = "Lending_Closed",$RecordType.Name = "Non_Lending_Closed",$RecordType.Name = "Non_Lending",RecordType.Name = "Lending"),
ISBLANK(TEXT(Loss_Reason__c)))

Thanks,
BD