One cause of this may be if the URL has additional variables. When framing a URL, some characters may cause the URL to not transmit all the information to the frame page.
If the URL you are using contains any ampersand (&) symbols, replace them with "_amp_". For example...
This is also the same with some other characters. If the link does not work properly, make sure to replace the following characters as follows:
- (dash) Replace with _H_
. (period) Replace with _P_
? (question mark) Replace with _Q_
The page being framed uses a session or cookie that is being lost when set in a frame. There is little that can be done in this situation, try opening the link in a new window instead.
The URL may contain invalid characters, such as a pound (#) symbol. Try removing the symbol and try framing it again.
The URL is incorrect or is missing the "http://".
The URL is hosted on a secure server, meaning the URL starts with https:// and the site has disabled the ability to frame it.