Welcome. What test and type of testing (strips, drops, tablets) are you doing? If you’ve never had fish before your pond will still need to cycle. You should notice a rise and then fall in ammonia. Next a rise and fall in nitrite. Since the ponds been going for a long time any wildlife visiting it will have contributed to the cycle so it is possible it will cycle fast, otherwise it is about a 6 week process.
it is a new environment for them, don’t feed them for the first few days, and then just a little every few days just to see if they are interested in eating. It may take a week or so for them to become comfortable in their new environment. Feeding very little is important initially until the nitrifying bacteria cycle has been established.
as mentioned, check for signs of critters visiting as well.