Unable to Install WSP on SP-2010 1:1:1 farm

Dear Experts,

Had a query, I am unable to Deploy a WSP file on SP-2010 Farm. Farm has 1 WFE, 1 APP, 1 DB. Initially the farm was 2 -Tier which we later made 3-tier by adding additional machine. I am getting Local Farm not accessible message, and some times access denied. I checked by Disabling User Acounts Group. and checked all server account was added to Local Admin Group. Previous Administrators were able to do so. Am I missing something.

Thanks,

Ajgar..