when you set custom excerpts in WordPress, there is no “read more” button out of the box. That is only available for automatic excerpts. If you want to have a “read more” button for custom manual excerpts, you would need to implement that accordingly, here you can find an example: How to add a read more Link to manual excerpts.
I try to add “read” more manually, but nothing work in “custom excerp post” only in normal. It’s shame but thanks for a reply.
As mentioned in the previous reply, the “read more” link for custom excerpts simply isn’t available in WordPress out of the box and you could implement it accordingly, for example as shown on the linked website (further modifications may be necessary). As soon as you’ve coded and implemented it correctly, the link will be available.
If you’re not familiar with coding and in case you need a developer for custom work, you could hire a freelancer or try to post the job here: http://jobs.wordpress.net/