Can't teach players new positions in fm 15

A common issue in Football Manager 2015!

If you're unable to teach players new positions, it's likely due to one of the following reasons:

1. Player's age: Players above a certain age (usually 28-30) may not be able to learn new positions. This is a game mechanic to reflect the limitations of older players.
2. Player's development: If a player's development is already maxed out, they may not be able to learn new positions. This is because their development is already complete, and they won't improve further.
3. Player's position: Some players may be too specialized in their current position and won't be able to learn a new one. For example, a striker may not be able to learn a defensive position like center back.
4. Team's squad depth: If your team has a strong squad with many players in each position, the game may not allow you to teach a player a new position to maintain squad balance.

To overcome this issue, you can try the following:

1. Look for younger players: Focus on developing younger players who have more potential for growth and may be more willing to learn new positions.
2. Use the "Train Manually" option: In the "Player Development" screen, select the "Train Manually" option to teach a player a new position. This may take longer, but it can be effective.
3. Use the "Position Change" option: In the "Player Development" screen, select the "Position Change" option to change a player's position. This may not work for all players, but it's worth a try.
4. Wait for the player to develop naturally: Sometimes, players will develop naturally and learn new positions as they gain experience and improve their skills.

Remember that teaching players new positions is a gradual process, and it may take time and patience to achieve the desired results.