Start with the log. Almost every answer is in it:

Valheim/BepInEx/LogOutput.log

When it loads correctly you will see:

[Info : MidgardPlus] Registered companion creature.
[Info : MidgardPlus] Registered Companion Horn.
[Info : MidgardPlus] Registered Reinforced Chest.

If those lines are missing, the mod did not load. Everything below explains why that happens.

The mod does not load at all

No MidgardPlus lines anywhere in the log. BepInEx never saw it.

• Confirm MidgardPlus.dll is in Valheim/BepInEx/plugins/, not in a subfolder of a subfolder, and not still inside the zip.
• Confirm BepInEx itself is running: the log should exist and mention other plugins.
• If you use a mod manager, launch through the manager. Launching from Steam skips the profile.

"Skipping [MidgardPlus] because of process filters"

You are on 1.1.0 or 1.1.1 on a dedicated server. Those builds declared a filter for valheim.exe only, so valheim_server.exe refused to load the plugin. Fixed in 1.1.2. Update.

Stuck in a respawn loop, or MissingFieldException on m_availablePieces

MissingFieldException: PieceTable.m_availablePieces

Jotunn 2.29.2 against current Valheim. It is a Jotunn problem, and it will keep your character cycling through respawn. Update Jotunn to 2.30.0 or newer.

MidgardPlus checks the Jotunn version on startup and logs a clear warning if it is too old, so you should see that named in the log rather than having to work it out.

The companion bag opens but the cursor vanishes

Fixed in 1.1.3.

In earlier builds the bag was pointed at the companion's own body inventory, which is a different shape than the 5x3 grid drawn over it, so the interface read past the end of its own slots and threw an error on every frame. The log filled with:

IndexOutOfRangeException: Index was outside the bounds of the array.
  at InventoryGrid.UpdateGui (Player player, ItemDrop+ItemData dragItem)

Because the interface aborted mid-update every frame, the cursor never appeared and nothing in the window could be clicked.

1.1.3 gives the bag its own inventory. Companions saved by an older build are repaired automatically the first time you open their bag, and you will see this in the log:

[Warning: MidgardPlus] Repaired companion bag: N items placed back in the grid, 0 did not fit

If more items were stored than a 5x3 bag holds, the extra ones cannot be placed and the count of what did not fit will say so.

Holding E does nothing on a companion

• Hold E, do not tap it. A tap toggles follow and stay.
• Make sure it is a MidgardPlus companion. Tamed wolves and boars have no bag.
• The bag will not reopen instantly after closing. There is a short cooldown, deliberately, so a held key does not reopen the window every frame.

My companion will not wear what I give them

• They will not swap down. If they are already wearing something better, a worse item in the bag is ignored on purpose, so a bag used for hauling does not strip their kit.
• Gear moves on a slow tick. Give it a few seconds.
• Nothing moves while the bag is open. Close it and wait.
• Only wearable types are used: weapons, bows, shields, helmets, chest, legs, gloves, capes, utility items and torches. Materials and food stay put, though food will be eaten when they are hurt.

Crafting from nearby chests is not finding anything

• It is off by default. Turn on Craft from nearby chests under 8 - Containers.
• Check Chest search range, default 20 metres.
• Chests currently open by another player are skipped.
• A companion's bag is not treated as a nearby chest, on purpose.

My settings are being ignored on a server

They are supposed to be. Every setting is host-authoritative, so a server's values replace yours while you are connected. Your own file is untouched and applies again once you leave. See Multiplayer and Dedicated Servers.

A setting changed but nothing happened in game

Some settings are read when something is created rather than continuously:

• Companion gear, Companion star level and health scaling apply to the next companion you call, not to ones already standing beside you.
• Day length in seconds takes effect on the next day cycle.

Multipliers are not stacking the way I expect

They never compound. Every multiplier is applied against a value captured once at startup, not against whatever the value currently is, so setting a multiplier twice does not square it and turning one off returns you exactly to vanilla.

Still stuck

Post in the Discord with:

• Your MidgardPlus version and your Jotunn version
• Whether you are solo, hosting, or joining someone
• The relevant part of BepInEx/LogOutput.log

Built by Odin the Red.