Hi Martin,
Give this a go , just change the dates between :
Select Top 1000000 tblAssets.AssetID,
  tblAssets.AssetName,
  tsysAssetTypes.AssetTypename,
  tsysAssetTypes.AssetTypeIcon10 As icon,
  tblAssets.IPAddress,
  tblAssets.Lastseen,
  tblAssets.Lasttried,
  tblAssets.Firstseen
From tblAssets
  Inner Join tblAssetCustom On tblAssets.AssetID = tblAssetCustom.AssetID
  Inner Join tsysAssetTypes On tsysAssetTypes.AssetType = tblAssets.Assettype
Where tblAssets.Firstseen Between '11-19-2020' And '11-20-2020' And
  tblAssetCustom.State = 1