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.block_product .block__body {
  display: -ms-grid;
  display: grid;
  -ms-grid-columns: 100%; /* для малых разрешений */
  grid-template-columns: 1fr;
  grid-gap: 20px;
}
.productCard {
  margin-bottom: 20px;/* вместно row gap для ie */
}

.productCard:nth-child(2) {
  -ms-grid-row: 2;
  -ms-grid-column: 1;
  -ms-grid-column-span: 1;
}
.productCard:nth-child(3) {
  -ms-grid-row: 4;
  -ms-grid-column: 1;
  -ms-grid-column-span: 1;
}
.productCard:nth-child(4) {
  -ms-grid-row: 5;
  -ms-grid-column: 1;
  -ms-grid-column-span: 1;
}
.productCard:nth-child(5) {
  -ms-grid-row: 6;
  -ms-grid-column: 1;
  -ms-grid-column-span: 1;
}
/* ... нужно все возможные прописать... */