Old unit is Vivint 345 hz installed the new IQ 4 345 hz
auto find wizard does not pick up
I have to manually enter sensors they show up as in system , but will not sound alarm or trip at all.
Does this mean I need new sensors?
This depends on the old panel model/exact model of the sensors.
If you had a 2GIG GC2 (Go!Control) panel as your old panel, yes the sensors will work. These sensors will be models like 2GIG-DW10, 2GIG PIR1, 2GIG-GB1
If you had the Sky Panel or anything newer, no, those would not be compatible. It sounds like this is likely the case, given your description.
If you are uncertain about the model of your old panel, you can verify by the model number of the wireless sensors. If you have 2GIG-DW11, 2GIG-PIR2, 2GIG-GB2 as any of the sensor model numbers, they are not compatible