getting no power electrically, even though battery shows fully charged

Follow the smaller battery positive wire to the under-hood fuse box. Check that connection to be sure it's clean and tight. Those have a tendency to work loose. Also follow the smaller negative battery wire to where it bolts to the body. Be sure that connection is tight and not rusty.

If that doesn't solve the problem, start with measuring the battery's voltage, then we'll figure out where to go next. If you need it, here's links to articles on using a digital voltmeter and test light:

https://www.2carpros.com/articles/how-to-use-a-voltmeter

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

The first article shows using an "auto-ranging" voltmeter. That's a feature found on the more expensive meters. You can find a perfectly fine voltmeter at Harbor Freight Tools for less than $7.00, or at Walmart or any hardware store. I can help you set it up if necessary.

For this test, a test light will work fine. Be sure to get an inexpensive one with a regular light bulb inside, not one of the newer fancy ones with lots of electronics. If we have to dig further into this, there are some tests where the test light can be more accurate and faster than using the voltmeter.