You can run maximum of 4-5 SSAS Tabular instances on single server
First: I hope I've missed something and would be very grateful if someone finds solution to overcome this limit. Microsoft has documented maximum number of instances for SQL Server database engine but for SSAS engines I couldn't find anything even after few hours searching. I have a customer whose business requirement is to run multiple SSAS instances on the same server. They've faced an issue when trying to start 5th SSAS Tabular instance on the same server.