I wouldn't throw in the towel just yet. I have had this issue multiple times with both escorts and SB's. Often it's a matter of nerves and performance anxiety. I'm in my 60's and I've found I must use Viagra prior to each session, and in most cases it works. But not always.  

So many factors go into getting and maintaining an erection and much of the time it's not even conscious. All the stars can align - you can feel totally relaxed and your partner is smoking hot and everything seems fine, but still you can experience no erection or continual erection.  

I've found for myself it's almost always psychological and based on performance anxiety and stress. Over time, if I'm with someone I'm sexually compatible with and comfortable with, the problem 'straightens itself out.'  

If I were you, I'd try different partners, as well as read up on the causes and cures of ED. Mostly don't overthink it as if you think too hard about it you can think yourself out of of being relaxed enough to allow it to happen.  

There may be factors in your life that are contributing to the issue, and those can be mitigated. These can include diet, anxiety, sleep issues, even physical health. Medications such as blood pressure statins, SSRI's [antidepressants] and a whole slew of other things can influence getting and staying hard.

Many men who are healthy and maintain a decent diet balance, get proper rest/exercise and are reasonably happy can have wonderful sex well into their 80's, so age is not always a bygone conclusion.

I'm guessing the problem will work itself out as you continue with this gal and possibly others and give it time.      

A lot of us have been there…
The most important element for me is having a partner who really WANTS to be fucked and wants you.
This becomes more complicated as we age and deal with P4P but good chemistry is possible, more so in the sugar world but sometimes with pros. Yes sometimes we don’t know if they are acting and sometimes it doesn’t matter. But there are women who are turned on by money, or by being a sex object or just by being with a successful older man.
It’s important to vet SBs and sometimes take some time to allow the attraction to develop.
I’m not a doctor or sex therapist but that’s my 2 cents.

I'm over 60 and I've experienced the same issue from time to time.  The posts above have great advice.  

 
I'll summarize it like this: It's all in your head.  

 
No, not that head, the big one on top. The key is to get out of your own way.  

 
Your body works, you know that. I'll guess you still get wood at random times when you are alone. So it's not a mechanical issue.  Try a date where sex is not expected but leave space for it to happen. Let her/ask her, to initiate it randomly.  Keep the focus on enjoying time with each other rather than warming up for a gymnastic event. Take your focus off of performing and place it on enjoying the moment when you are with a beautiful young sexy horny woman.  

 
It's not all on you, of course. The more enthusiastic she is the better. Like Papa Sweet noted, there is nothing more stimulating than a hot babe who WANTS to fuck YOU!   Ultimately, you may indeed get bored or lose the spark with a specific partner.  You need to be a little bit selfish here, as repeated dates with no happy ending are just a poor use of your budget.  

 
I'll suggest you have a discussion with her about these ideas, if you still want to try with her.  Otherwise, perhaps a 2-4 week break is a good idea, and you can reset with a new partner.  I have done that more than once.  

Life is good.  

 
The Cat

One has already been mentioned
- Stress in life situation. Could be work, home, friends/family.
- Effect of meds, especially if new, or
- Your body is telling you you don't really like her/she doesn't arouse you.

But if not the above, then I would go see a doc. Could be sign of incipient circulatory or cardiac issues.

First, can you get it up and drop a load watching your favorite porno? Yes, ok that’s good! Next make an appointment with a provider with plenty of great reviews that you find to be incredibly sexy! Can you get it up and drop a load with her? OK good! Now find a new SB that you find to be really hot and try her BCD!  Did you get it up and drop a load this time? If the answer is no for steps one or two, go see a doc. If it is no for step three, you may not be finding SB’s that are hot enough. Perhaps you should stick to pros that you find to be sexy with the expertise to get you off! You are way too young to throw in the towel!

Thank you all for the sage advice. Through a process of elimination (roughly along the lines of what blue5361 proposed), I've identified the issue as nerve damage due to excessive bike riding over the past 4 months.