You will need to upgrade your SRM to version 6.5.1, since your current SRM is not compatible with the vCenter 6.5 U1, see: VMware Product Interoperability Matrices
The following VMware KB article shows the correct upgrade sequence: Update sequence for vSphere 6.5 and its compatible VMware products (2147289) | VMware KB
You will need to upgrade your SRM to version 6.5.1, since your current SRM is not compatible with the vCenter 6.5 U1, see: VMware Product Interoperability Matrices
The following VMware KB article shows the correct upgrade sequence: Update sequence for vSphere 6.5 and its compatible VMware products (2147289) | VMware KB