No crank

You need to give us more of a "step by step." Power WHERE? WHEN?

Can you get it to crank by jumpering across the starter terminals? If not, then the battery, main cables, and starter, and possibly engine are your concern

Will it crank when jumpering across the two large terminals of the starter relay?

Is the starter relay grounded? MUST be on a 69 stick!!! OR do you have the RIGHT relay? How many terminals? 3? 4?

If it cranks when jumpering across the two big relay terminals, then disconnect the (should be just one) "push on" terminal, and jumper from the big battery stud to the push on terminal.

If it DID crank when jumpering the battery stud/ solenoid terminal, but now does NOT crank when jumpering to the "push on" terminal then the relay is bad.

If it DOES crank in all cases, then hook the "push on" terminal back up, back probe the connector with your meter, and twist the key. You should get "same as battery" and the car should crank. If the voltage here is low, or none, then you have problems in the under dash harness, or the bulkhead connector