You did not fully upgrade your walls
It is equally important to upgrade your walls along with upgrading your town hall. Many players upgrade the town hall to the maximum but do not upgrade the walls to the maximum, which is essential.
You are ignoring air defences
You cannot just keep air defences your last priority to upgrade. As many players use dragons and air units as their army, we need to have robust air defence to tackle them.
You upgraded your town hall too early
The most significant aspect of this game is to maintain balance. If you lose balance, you lose against the attacker. This is what happens with many Clash of Clans players, as they upgrade their town hall so early that they do not get a chance to upgrade their defences appropriately, which leads them to lose the game.
You advanced to a high league expeditiously
You should always expect more influential players to speedily attack your base if you are advanced to a high league. It is better to wait, invest some time, and become eligible to compete in the advanced competitions to a particular league before you finalize you are entering those leagues.
Inefficient village layout
It is vital to lay out your village meticulously. You can still lose if your defence and town hall is robust and your village layout is improper. (See How to make a successful attack in Clash of Clans?)
You don’t have castle troops
Having large castle troops is a significant factor that facilitates destroying more massive armies more swiftly. One should make sure that they have adequate castle troops in their castle if their defences lose often.
Your splash defences aren’t upgraded
Splash Defences include Towers, and Mortars should be fully upgraded to help you become stronger and make the large group of enemies possibly lose against you. (See How to Defeat Clan Castle Troops in Clash of Clans)
Your defences are not well balanced
Always make sure that any point of the map is covered by Mortar fire, air defences, and of course, ground defences. The attacker can easily find a vulnerable point of the missing gap if you cannot maintain proper balance.
You are attracting strong players
It is highly recommended never to store too much Gold or Elixir as they won’t turn favourable. Instead, they will allure strong players towards your town hall and maximize the chances for you to lose. Hence, a player should manage and allocate their resources in a well-planned manner.
You are using single walls
It is essential to ensure that your base is not surrounded by a single wall, increasing the chances of losing against the attacker. There should be at least more than a single level of walls so that it becomes difficult for an attacker to reach important buildings that are elementary for the kingdom.
Your defences are widely spaced
It makes it more accessible for the attacker to hit your town hall if you placed your defences far from each other. Instead, it should be placed so that the opponent finds no room for attacking, and it becomes harder for the attacker to destroy the village.
Why does my defense keep losing in Clash of Clans?
Any idea why my defense keeps losing? Why does my defense keep losing in Clash of Clans?