Train tracking app in Spain

Yes--Renfe.

Some seem to have trouble purchasing tickets from them and use Trainline instead. That's what i did for my March trip earlier this year.

Trainline connects to Renfe so you can select seats when needed and receive updates about any cancelled or delayed trains.

I have been having better luck booking on Renfe app on my phone than on their website.
Also if you are trying to book after banking hours in Spain. The securities’ checks between their bank and yours(credit cards) may be the disruption. I called my CC after getting a rejection notice on my purchase from Renfe and the customer service rep told me they did not see a transaction try to process so it halted somewhere on the Spanish side.
Try booking in US a.m. hours weekdays ( it’s amazing that this could be the issue, but I haven’t had the issue since I self imposed that on my own booking attempts!)

Renee’s app works well. If you have multiple trips to book, save yourself some time and create an account and register the passengers’ info for everyone traveling with you. Then you can just pick the names when booking the tickets and the info will link automatically, no need to retype.

Payment for tickets can be iffy. I recently purchased 3 sets of tickets (on a Sunday morning). Two of them went through on my Visa card with no issue. The third wouldn’t. I switched to PayPal (where the same credit card is linked) and had no issue paying for the third set of tickets. This strategy has worked well for me over many trips — when my actual card doesn’t work, I just switch to PayPal (or start there in the first place when I remember).