A "please try again later" is frequently caused by a time out error when trying to connect to a server. Either Apple's servers are down or too much traffic, or something on your own network is blocking the connection. Do you have any firewalls or antivirus software set up, that could be intercepting the connection to Apple's servers?
It could also be a problem with the authentication or your AppleID.
Does the Mac App Store work for you, for example? Can you purchase some free app from the AppStore? If there should be any problem with your Apple ID or payment mthod it is easier to fix by trying to buy directly from the App Store.
Are you using two-factor authentication?
This can interfere with Photos trying to access Apple's servers.
If the two-factor-authentication is interfering it usually helps to create an app-specific password for the app you are using, in this case Photos. Then you can keep the two-factor authentication active. It helped in similar cases, for example Mail, see this discussion:
Re: I am using iPhoto version 9.6 and I can no longer get an email sent with a photo attached. I get an error message saying the email did not go through because the server did not reply. I can send the photo with Mail. Help!in response to Gary Kissler
This solution is for those of you using 2-step verification for your Apple ID and are using iCloud as the mail server that you are trying to mail photos with.
I too had this issue. The problem in my case occurred because I had setup 2-step authentication for my Apple ID. If you have done this then you will get the error message "the mail server did not recognize your email/password...". To solve the problem go to:
https://appleid.apple.com
- Click "Manage Your Apple ID"
- Verify your identity with the device you selected (if this step does not show up then you have not likely set up 2-step authentication and this is not your solution)
- Click Password and Security in the left column
- Click Generate an app-specific password
- Enter iPhoto as the name of the app
- Copy the password and paste this into the password box in iPhoto where you would normally enter your apple ID (in the mail account section in iPhoto preferences).
And...voila' (I hope)
