Ack! Verizon Int’l plan, cannot figure out how to dial

Most German phone numbers start with the country code +49 and then look something like 0555 555 55 55. Try dialing 49 555 555 55 55. or just 0555 555 55 55. If that doesn't work try 0049 555 555 55 55. And last, if that doesn't work try 001 49 555 555 55 55. One of those should work. The problem is knowing if your sim is being recognized as being in Europe, of if you're still dialing internationally from the USA.

When traveling international, to call home to the US, dial +1 and the 10 digit number. For calls within Germany, dial +49 and the local number you are calling. Dial +/plus sign first then the phone numbers, and + may be dialed by long holding the zero.

On your phone, is "data roaming" turned on? You need to do this to connect to international cell sites.

Even if it is not turned on you can make emergency calls which is why I ask giving what you are hearing.

Dial +49 30 12345678

The "+" you will get by long press on the button the "+" is shown.
49 is country code for Germany
30 is national code for Berlin (normally 030 but the leading zero is left out when country code is leading)
12345678 is the local number you want to dial.
The spaces you can leave out; I just added them here for better overview.

This is ITU-T E.123 standard working in all networks.

As frank said make sure first that you have roaming turned on

This, from Verizon:

https://www.verizon.com/tariffs/PDFViewer.aspx?doc=168575

"Direct-dial international calls are placed in a similar manner as domestic long distance calls. An
international phone number is generally made up of a country code, a city and the local exchanged
number.
To Place a Call an International Call
1. Dial 011.
2. Dial the country code.
3. Dial the phone number you wish to reach.
Example: To call a number in France, first dial the International Dialing prefix of "011", then dial the
country code "33", then dial the phone number."

You need to do what Mark K said (after making sure roaming is on)

+49 then the number

As stated above turning roaming on is essential. Also, remember to turn roaming off when you return to your country.