"Read more" link not appearing.

Hello all!

I put this tag in a post:

<!–more–>

Only the text before the tag appears on the home page, but there is no link of any kind. It simply comes to an end where the tag should be.
(This is on free themes that show it with the correct “Read more” tag on previews and demos.)

But on some themes it appears as “Continue reading…” which is good. But if I try to change the text this way:

<!–more Read more–>

It remains as “Continue reading…”.

What am I not doing?

I would be grateful for any help!