in order to use PVDM2 on IOS 15, you must use router 2900 or above. I mean router 2800 whith pvdm2 not working well on IOS 15. so if you have Router 2800 with pvdm2, don't use IOS 15, instead use ios 12.3(8)T4. I'm currently using ios Version 12.4(5b...